Proc. Nati. Acad. Scn. USA Vol. 76, No. 6, pp. 2546-2550, June 1979

Biochemistry

Asymmetric and globular forms of acetylcholinesterase in mammals and birds (sedimentation coefficients/quaternary structure/collagenase/Stokes radius/low-salt aggregation)

SUZANNE BON, MARC VIGNY, AND JEAN MASSOULIE Laboratoire de Neurobiologie, Ecole Normale Suphieure, 46, rue d'Ulm, 75230 Paris Cedex 05, France

Communicated by David Nachmansohn, February 26, 1979

ABSTRACT We have identified six molecular forms of acetylcholinesterase (AcChoE; acetylcholine hydrolase, EC 3.1.1.7) in extracts from bovine superior cervical ganglia. We show that three of them resemble the collagen-tailed forms of Electrophorus AcChoE in their hydrodynamic parameters, low-salt aggregation properties, and collagenase sensitivity. The six molecular forms of bovine AcChoE appear structurally homologous to the six forms of electric fish AcChoE that have previously been characterized. They include globular molecules (monomers, dimers, and tetramers) and asymmetric aggregating molecules that possess a collagen-like tail associated with one, two, and three tetramers. We propose to call the globular forms GI, G2, and G4 and the asymmetric forms A4, A8, and A12, the subscripts indicating the number of catalytic subunits. In spite of quantitative differences in their molecular parameters, the AcChoE forms from rat and chicken are clearly homologous to those of bovine AcChoE. Thus the nomenclature we introduce is very probably valid for the main AcChoE molecular forms, at least in vertebrates, and should help to clarify structural relationships and homologies among them. This model, however, does not claim to represent entirely the complex polymorphism of AcChoE, because more or less hydrophobic variants of the G forms have been observed, and because other molecular associations cannot be excluded. We discuss the significance of the globular and collagen-tailed structure for the molecular localization of AcChoE.

MATERIALS AND METHODS The major part of the results presented here were obtained with AcChoE from bovine SCG. For preparative purposes, we solubilized the enzyme in several steps: the nonaggregating water-soluble forms were first extracted in 10 vol of low-salt buffer (10 mM Tris-HCl, pH 7). The pellet obtained after centrifugation (20,000 X g, 15 min) was then extracted in saline buffer (1 M NaCl/50 mM MgCl2/10 mM Tris-HCI, pH 7) in order to solubilize the aggregating forms, which were concentrated by an isopycnic centrifugation in a CsCl gradient, as described (10). The individual molecular forms were then separated by centrifugation in a sucrose gradient, in saline buffer. Experiments were also performed on rat tissues (diaphragm, sternocleidomastoidian and soleus muscles, and SCG) and chicken tissues (leg and posterior latissimus dorsi muscles and ciliary ganglia). These tissues were homogenized in saline buffer containing 1% Triton X-100, which allows a quantitative solubilization of all molecular forms, because of the small amount of tissue available in the case of the ganglia, or of the low AcChoE activity of the extracts in the case of the muscles. The analytical methods used in this work were identical to those already described for Electrophorus AcChoE (9, 18, 20). Pure collagenase type I from Clostridium histolyticum was a gift of P. Taylor (16, 17). Collagenase form III, chromatographically purified and free of detectable nonspecific proteases, was obtained from Advance Biofactures Corporation (Lynbrook, NY) and used in the presence of 5 mM CaCl2/100 mM Tris-HCI, pH 8.

Acetylcholinesterase (AcChoE; acetylcholine hydrolase, EC 3.1.1.7) of avian and mammalian tissues occurs in several molecular forms, as defined by sedimentation analysis (1-7), in a manner similar to the enzyme forms of Electrophorus and Torpedo electric organs (8-10). The lighter forms appear to be biosynthetic precursors of the heavier ones (11). The fastsedimenting, or "heavy" forms, 17S in mammals and 20S in chicken, have stimulated considerable interest because their presence in skeletal muscle appears to be dependent upon innervation (1, 3, 5, 12). Previous studies have not revealed any obvious homology between these forms from higher vertebrates and those of electric fish AcChoE. In particular, it has not yet been shown whether some of these molecules possess a collagen-like tail, similar to that observed in electric organ enzymes (13-17). This structural component appears to play a key role in the low ionic strength aggregation of these enzymes (14, 18, 19). In this paper we describe the properties of the molecular forms of AcChoE from bovine superior cervical ganglia (SCG). Our data allow us to conclude that their quaternary structure closely parallels that already established for electric organ enzymes (9).

RESULTS AND DISCUSSION

Low-Salt Soluble and Insoluble Molecular Forms from Bovine SCG. We observed a reversible precipitation in a saline extract of bovine SCG when the salt concentration was reduced by dialysis, and a pellet containing a fraction of AcChoE activity could be separated by low-speed centrifugation. Fig. 1 shows a sedimentation analysis, in high-salt conditions, of the total extract as well as of the low-salt soluble and insoluble components. It is clear that these components correspond to distinct molecular forms, which we will call globular or G forms (GI, G2, G4) and asymmetric or A forms (A4, A8, A12), for reasons that will become apparent later. The sedimentation patterns shown in Fig. 1 have been obtained in the presence of Triton X-100; in these conditions, the sedimentation coefficients of GC and G2 are markedly decreased, ensuring a better resolution between these forms and A4. The sedimentation coefficients

The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact.

Abbreviations: AcChoE, acetylcholinesterase; SCG, superior cervical ganglia. 2546

Biochemistry:

Bonet al.

Proc. Natl. Acad. Sci. USA 76 (1979)

2547

Table 1. Sedimentation coefficients, Stokes radii, and molecular weights of bovine SCG AcCboE molecular forms

Sedimentation coefficient, S

Stokes radius, nm

Molecular weight

3.7

Go

4.8 7.8 10.5

6.1 8.1

71,000 191,000 341,00()0

A4 A8 A12

8.7 13 17.1

Form

GI G2

o

B

A

Hydrodynamic Parameters of the AcChoE Forms of Bovine SCG: Asymmetric Character of the A Forms. As shown in Fig. 4, the elution of the A forms from a Bio-Gel A-15m column revealed much higher Stokes radii than those of the G forms (Table 1). This was particularly significant in the case of

A8~~

10

20 Fraction

30

Fiu. 1. Low-salt soluble and insoluble forms of bovine SCG AcChoE. An extract of bovine SCG in saline buffer was fractionated into low-salt soluble and insoluble components after dialysis against low-salt buffer. The low-salt insoluble material was redissolved in saline buffer. The total extract (A) and the soluble (-) and low-salt insoluble (A) components (B) were analyzed by centrifugation in .5-20% (wt/vol) sucrose gradients (1% Triton X-100/0.1 mg of bacitracin per ml/I M NaCI/50 mM MgCl2/10 mM Tris-HCI, pH 7), using a Beckman SW 41 rotor, at 40,000 rpm, for 21 hr at 40C. The AcChoE activity is plotted on an arbitrary scale, as a function of the fraction number, which represents the distance from the bottom of the tube. Escherichia coli 0-galactosidase (16S), beef liver catalase (11.4S), and horse liver alcohol dehydrogenase (4.8S) were used as sedimentation standards.

of the various forms, in detergent-free saline gradients are given in Table 1. Similarity between the Low-Salt Precipitation of Bovine SCG AcChoE and the Aggregation of Electrophorus Asymmetric Forms. The low-salt precipitation of bovine AcChoE had the same ionic strength dependence as the aggregation of the Electrophorus enzyme (Fig. 2). These purified electric organ enzymes, depleted of aggregating agent (17), associated with the precipitate, behaving exactly like the bovine A forms, but the tetrameric form remained soluble. In effect, interaction of an isolated nonprecipitating bovine A12 fraction with polyanions was similar to that of Electrophorus AcChoE (19): the fraction formed small 20-30S aggregates with chondroitin sulfate, but hyaluronic acid was inefficient at 10-fold higher levels. Moreover, the low-salt precipitation was prevented by acetylation (18) as illustrated in Fig. 3B for the A12 and A8 forms, and could not be restored by addition of a nonacetylated diisopropyl fluorophosphate-inhibited extract. As in the case of Electrophorus, collagenase specifically modified the bovine A forms, yielding molecules that sedimented faster by about 1.5 S and no longer aggregated (Fig.

:3C).

15.5

Sedimentation coefficients and Stokes radii were determined in sucrose gradients (cf. Fig. 1) and in a Bio-Gel A-15m column, using a detergent-free saline buffer. In the presence of 1% Triton X-100, the apparent sedimentation coefficients of GI and G2 were shifted to, respectively, 3.5 S and 6.1 S. The molecular parameters of the A forms were not modified by the detergent within experimental precision. Apparent molecular weights were determined by assuming that they are proportional to the product of the sedimentation coefficient and the Stokes radius with the same proportionality constant as for the Electrophorus enzymes (9, 14).

G4

2

453,000 747.000 1,062,000

13.0 14.35

the A4 form, which sediments slower (8.7 S) than G4 (10.5 S), indicating a highly asymmetric structure. The low-salt aggregation properties of these molecules, together with their sensitivity to collagenase, suggest that their asymmetric character might be due to the presence of a collagen-like tail similar to that of the Electrophorus AcChoE. The action of collagenase on the isolated A forms of bovine AcChoE is summarized in Table 2. At 30'C the reaction is limited, producing molecules that have lost their aggregating properties and some of their asymmetric character. At 370C, the reaction proceeds further, finally converting all three forms into G4, which may then be considered as a common dissociation product of the asymmetric molecules. We have, however, isolated intermediate transformation products from As and A12. I

I

, ,

, ,

I

I

,

I

I

, I1

AF

-

10

I

X A

a)50 0

0

0.1

0.2

0.3

MgCI 2 M FIG.. 2. Dependence of low-salt precipitation or aggregation upon salt concentration. A---A, Proportion of dissociated asymmetric forms of Electrophorus AcChoE (from ref. 17). A----A, Fraction of Electrophorus AcChoE in a low-speed supernatant (10,000 x g, 10 min) in the presence of a diisopropyl fluorophosphate-inhibited low-salt insoluble fraction from bovine SCG. 0- --, Fraction of bovine SCC AcChoE (low-salt insoluble component) in a low-speed supernatant under the same conditions as for Electrophorus.

2548

Biochemistry:

Bonet al.

Proc. Natl. Acad. Sci. USA 76 (1979)

Ac~hoElAI2A8 A4Fib1 jI-GaI1Cat1 G4 G2

xVe

G.

Vt j

:> U w

0

U

|.. . , , ; ~~~'

6

__~'

70

,

150

100 Fraction

FIG. 4. Gel-filtration chromatography of bovine SCG molecular forms of AcChoE. Chromatography was performed in a Bio-Gel A-15m column in detergent-free saline buffer. The arrows indicate the exclusion volume Ve (phage T4) the total volume Vt [FeK4(CN)61, and the position of the marker proteins Electrophorus AcChoE (D, or A12, form) (15.6 nm Stokes radius), fibrinogen (10.7 nm), E. coli f3-galactosidase (8.2 nm), and catalase (5.2 nm).

0

C. can be related masses.

10

20 Fraction

30

FIG. 3. Effect of acetylation and collagenase treatment on the aggregating forms of SCG AcChoE. Bovine SCG were first homogenized in low-salt buffer (1/10 wt/vol), in order to remove some of the nonaggregating forms of AcChoE. Aliquots of a second extract, in saline buffer, were acetylated or treated with collagenase and then dialyzed against 0.01 M Tris-HCl, pH 7. The supernatant was analyzed in low-salt sucrose gradients (0.1 mg of bacitracin per ml/50 mM Tris-HCl, pH 7) at 40,000 rpm for 15.5 hr. (A) Control; (B) acetylated extract (cf. ref. 18); (C) collagenase-treated extract (20 jIg of collagenase type III in 1 ml of extract, 30 min at 30'C).

Molecular Weights and Quaternary Structure of the A and G Molecular Forms. The isopycnic density of bovine AcChoE in a cesium chloride gradient is identical for all molecular forms (1.31 g/cm3) and very close to that of Electrophorus AcChoE (1.33 g/cm3) (20). We therefore assumed that the same proportionality constant between the sedimentation coefficient X

to that of A4 by addition of one and two tetramer These molecules, like the 14.2S and the 18.4S forms of Electrophorus AcChoE, are therefore considered to contain, respectively, two (A8) and three (A12) tetramers. The molecular weights of the various molecules, as derived in Table 1, have been plotted as a function of the number of catalytic subunits (Fig. 5). It may be seen that the points representing the A forms define a straight line, the slope of which corresponds to the molecular weight of the monomer. This line intersects the vertical axis at a value, 140,000, that gives an approximation for the molecular weight of the noncatalytic element in these molecules. The derivatives obtained from the A forms by treatment with collagenase at 30'C differ very little in mass from the original molecules. In contrast, the fast-sedimenting molecules (20 S, 15.7 S) obtained at 370C have significantly lower molecular weights (Table 2), and the corre-

sponding points fall

very

close to the line of the G2 and G4

globular forms. These molecules therefore appear to have lost the major part of the tail. Asymmetric Molecular Forms of AcChoE in Rat and Chicken Tissues: Structural Homology with the Molecular Forms of Bovine SCG. We observed a reversible precipitation, at low ionic strength, of the "heavy" forms of rat (17S and 13S) and chicken (20S and 14.8S) AcChoE forms. The salt concentration dependence of this precipitation was essentially identical Table 2. Sedimentation coefficients, Stokes radii, and molecular weights of collagenase-modified asymmetric forms of bovine SCG AcChoE

Stokes radius products and molecular weights applies for both

species (9), and this enabled us to derive the molecular weights given in Tables 1 and 2. The molecular weight value (71,000) obtained for the smallest globular form, G1, is very similar to the molecular weight of the catalytic subunit of a G4 preparation from bovine SCG (21). If the GI form is therefore considered as a monomeric molecule of AcChoE, then the G2 and G4 forms are respectively dimers and tetramers, possibly associated with an additional component, because their molecular weights appear to exceed significantly the expected values (Fig. 5). We have shown that the A forms probably contain a collagen-like tail and can be dissociated into G4 by collagenase at 370C. Because the mass of the A4 molecule is only slightly larger than that of a tetramer, we conclude that it consists of one tetramer linked to the tail. The masses of the two heavier A forms

Stokes

Incubation

Sedimentation

radius,

Molecular

temperature, 0C

Form

coefficient, S

nm

weight

30

A4 A8 A12

9.6 14.3 18.5

11.5 13

442,000 745,000 1,008,000

A4 A8 A12

10.7 15.7 20

8.15 10.75 12.2

37

13.6

349,000 676,000 978,000

Incubation with collagenase type I (approximately 10 ,g/ml) was for 30 min at 30'C and for 15 min at 370C (cf. Figs. 5 and 6). The experimental conditions were the same as for Table 1. The molecule obtained from A4 at 370C is indistinguishable from G4 within experimental errors. It also represents the end product of the action of

collagenase on

A8

and A12 at this temperature.

Biochemistry:

Proc. Natl. Acad. Sci. USA 76 (1979)

Bonet al.

2549

0

x

0.5

,

,

, , , I

0

0)

Q

10 5 Number of catalytic subunits

15

FIG. 5. Relationship between molecular weights and hypothetical number of catalytic subunits. 0, G forms; *, A forms; 0, collagenase-modified A forms (30'C); A, collagenase-modified A forms (370C). The points corresponding to the A forms determine a straight line, the slope of which corresponds to the molecular weight of the subunit. Its intersection with the vertical axis gives an approximation for the molecular weight of the collagen-like tail of these molecules (140,000). The G2 and G4 forms appear to slightly exceed in molecular weight the expected value.

to that illustrated in Fig. 2 for the Electrophorus and bovine enzymes. It was abolished by acetylation in the same manner, and treatment with collagenase produced faster-sedimenting, low ionic strength soluble derivatives of the heavy forms (data not shown). We therefore conclude that the low-salt insoluble component of AcChoE represents asymmetric, collagen-tailed molecules (A forms), while the soluble component corresponds to globular molecules (G forms). The molecular properties of the various forms of AcChoE from rat and chicken are summarized in Table 3, together with some data on human muscle AcChoE (22). Having recognized the existence of several asymmetric forms, which possess similar interaction properties, as well as a characteristic structure, we asked whether they would be physiologically equivalent, for example in their specific localization at the neuromuscular junctions in rat skeletal muscles. Fig. 6 shows that this is indeed the case for the A8 form, in the sternocleidomastoidian muscle. This form was a minor component, amounting to only about 10% of the A12 form. In this experiment, we were not able to detect the A4 molecule. Table 3. Sedimentation coefficients and Stokes radii of chicken, rat, and human AcChoE molecular forms Sedimentation coefficient, S Stokes Human radius, nm Rat (22) Chicken Rat Form Chicken 4 6.5 3.5 3.5 7.4 GI 6.5 6 6 9.4 G2 11.5 11 9.9 10.8 9.9 G4 9.5 8.8 A4 14.8 13.3 15.5 13 A8 16.2 16.7 18.15 20 16.7 A12 These data were obtained in Triton/saline buffer (1% Triton X100/1 M NaCl/50 mM MgCl2/10 mM Tris-HCl, pH 7), using Bio-Gel A-50m and Bio-Gel A-15m for the A and G forms, respectively. We have not been able to detect any molecular form corresponding to A4 in chicken extracts.

Fraction FIG. 6. AcChoE forms in neural and aneural regions of rat sternocleidomastoidian muscle. Sedimentation analysis as in Fig. 1. A-,, Endplate-containing section; 0-0, endplate-free section.

CONCLUSION We have shLown that the molecular forms of AcChoE that can be solubilized from avian and mammalian tissues belong to two well-defined classes. The G, or globular, forms represent monomers (G1), dimers (G2), and tetramers (G4) of the catalytic subunit. These forms are soluble in low-salt conditions, and are not sensitive to collagenase. In contrast, molecules of another group (A forms) become insoluble in low-salt conditions, and this phenomenon shares a number of features with the low-salt aggregation of the collagen-tailed forms obtained from Electrophorus electric organs (18, 19): (i) both phenomena depend on salt concentration in the same manner; (ii) they are equally abolished by acetylation of the enzyme; (iii) polyanions interact with the isolated enzymes in a similar way, and (iv) Electrophorus tailed forms coprecipitate with the enzymes of higher vertebrates when added to a tissue extract. In addition to aggregating, the A forms are sensitive to collagenase, which produces derivatives with higher sedimentation coefficients and lower Stokes radii, and this occurs in discrete steps in a temperature-dependent fashion. We used a comparative method, based on their hydrodynamic parameters, to obtain the molecular weights of the forms of the bovine AcChoE molecules. The values obtained led us to conclude that these molecules correspond to the same quaternary associations of subunits as established for the Electrophorus AcChoE forms, although we have not yet been able to determine the number of catalytic sites of the bovine AcChoE forms; i.e., we have not shown that all globular subunits are catalytically active as in the case of Electrophorus (23). The relationships of the bovine molecular forms, as illustrated by their sequential disruption by trypsin, confirms their parallelism with the Electrophorus enzymes (21). Our results suggest that the structural homology between the molecular forms of AcChoE extends to all vertebrates, from the elasmobranch Torpedo and the teleost electrophorus to mammals and birds. We think that it may be useful to express the homology explicitly by a unified nomenclature that distinguishes globular forms (GC, G2, G4) and aggregating forms (A4, A8, A12), qualifying each form by its probable number of catalytic subunits. This basic structural framework does not claim, however, to represent the totality of AcChoE polymorphism. We have previously shown the existence of variants of distinct solubility or electrophoretic properties among the G forms (2, 4). Chicken AcChoE appears somewhat more complicated. Rotundo and Fambrough, whose results on the low-salt insolubility and collagenase sensitivity of the 20S form are in excellent agreement with ours, obtained some new forms by incubating this molecule

2550

Biochemistry:

Bonet al.

with trypsin (24). We have made similar observations and will discuss elsewhere the relationship of these modified molecules and the native structures examined here. In addition, the same authors showed that chicken muscle cells in culture secrete 15S and 9S forms, which cannot be interpreted at present irt terms of quaternary structure (24). The A12 molecule corresponds to the heavy form that has been shown to disappear from denervated rat and chicken muscles (1, 3, 5, 25, 26). The other two asymmetric forms have not been described previously. The A8 form, however, can be recognized in some of the published sedimentation patterns, in the case of the chicken muscle (5). In rat muscle, we observed that it is also restricted to the endplate region, and, although this could not be verified for the very minor A4 form, it is likely that this is true for the three asymmetric forms. In human muscle, the high proportion of asymmetric forms that exists in some individuals makes it possible to demonstrate the existence of the three forms-A12, A8, and A4-even in unfractionated extracts [in this case, however, they are not preferentially located at the endplates (22)]. The relative importance of A and G molecular forms is very variable in different tissues from a given species and in homologous tissues from different species. For example, the G forms appear essentially as degradation artefacts in Electrophorus electric organ extracts, but are predominant in tissues of mammals and birds (e.g., figure 1 and 7). The A forms even seem to be entirely absent from the central nervous system of these animals (2, 6). We have found that Triton X-100 does not modify the molecular parameters of the A forms and does not interfere with their low-salt precipitation. As in the case of the Electrophorus enzymes, we therefore suggest that the A forms are not membrane bound but are anchored via ionic interactions in the basal lamina-e.g., within the neuromuscular synaptic cleft (14, 15, 27). In contrast, the hydrodynamic properties of some variants of the G forms are modified by nonionic detergents, indicating that the G forms may be involved in hydrophobic interactions, as will be examined in a further publication. The G4 form has in fact been shown to be externally associated with the plasma membrane, in neuroblastoma cells (unpublished data). Thus ionic and hydrophobic interactions seem to be responsible for the molecular localization of the A and G forms, respectively. These various forms of AcChoE are probably designed to meet distinct physiological requirements. We are grateful to Dr. Jeanine Koenig for providing the neural and aneural sections of rat muscle, to Dr. Palmer Taylor for the gift of pure collagenase, and to Dr. Vittorio de Franciscis for phage T4; we thank

Proc. Natl. Acad. Sci. USA 76 (1979) Mr. Pierre Allemand for his technical assistance and Mrs. Solange Duchatel and Jacqueline Pons for typing the manuscript. This work was supported by grants from the Centre National de la Recherche Scientifique, the Delegation Generale a la Recherche Scientifique et Technique, and the Institut National de la Sante et de la Recherche

Medicale. 1. Hall, Z. (1973) J. Neurobiol. 4,343-361. 2. Rieger, F. & Vigny, M. (1976) J. Neurochem. 27, 121-129. 3. Vigny, M., Koenig, J. & Rieger, F. (1976) J. Neurochem. 27, 1347-1353. 4. Gisiger, V., Vigny, M., Gautron, J. & Rieger, F. (1978) J. Neurochem. 30,501-516. 5. Vigny, M., Di Giamberardino, L., Couraud, J. Y., Rieger, F. & Koenig, J. (1976) FEBS Lett. 69, 277-280. 6. Marchand, A., Chapouthier, G. & Massoulie, J. (1977) FEBS Lett. 78,233-236. 7. Di Giamberardino, L. & Couraud, J. Y. (1978) Nature (London) 27, 170-172. 8. Massouli6, J. & Rieger, F. (1969) Eur. J. Biochem. 11, 441455. 9. Bon, S., Huet, M., Lemonnier, M., Rieger, F. & Massoulie, J. (1976) Eur. J. Biochem. 68,523-530. 10. Rieger, F., Bon, S., Massoulie, J., Cartaud, J., Picard, B. & Benda, P. (1976) Eur. J. Biochem. 68,513-521. 11. Rieger, F., Faivre-Bauman, A., Benda, P. & Vigny, M. (1976) J. Neurochem. 27, 1059-1063. 12. Koenig, J. & Vigny, M. (1978) Nature (London) 271, 75-77. 13. Johnson, C. D., Smith, S. P. & Russell, R. L. (1977) J. Neurochem. 28, 617-624. 14. Bon, S. & Massoulie, J. (1978) Eur. J. Biochem. 89,89-94. 15. Anglister, L. & Silman, I. (1978) J. Mol. Biol. 125, 293-311. 16. Taylor, P., Jones, J. W. & Jacobs, N. M. (1974) Mol. Pharmacol. 10,93-107. 17. Lwebuga-Mukasa, J. S., Lappi, S. & Taylor, P. (1976) Biochemistry 15, 1425-1434. 18. Cartaud, J., Bon, S. & Massoulie, J. (1978) J. Cell Biol. 77, 315-322. 19. Bon, S., Cartaud, J. & Massoulie, J. (1978) Eur. J. Biochem. 85, 1-14. 20. Bon, S., Rieger, F. & MassouliW, J. (1973) Eur. J. Biochem. 35, 372-379. 21. Vigny, M., Bon, S., Massoulie, J. & Gisiger, V., (1979) J. Neurochem., in press. 22. Carson, S., Bon, S., Vigny, M., Massoulie, J. & Fardeau, M. (1979) FEBS Lett. 97, 348-352. 23. Vigny, M., Bon, S., Massoulie, J. & Leterrier, F. (1978) Eur. J. Biochem. 85, 317-323. 24. Rotundo, R. & Fambrough, D. (1979) J. Biol. Chem., in press. 25. McLaughlin, J. & Bosmann, B. H. (1976) Exp. Neurol. 52, 263-271. 26. Sketelj, J., McNamee, M. G. & Wilson, B. W. (1978) Exp. Neurol. 60,624-629. 27. Dudai, Y. & Silman, I. (1974) J. Neurochem. 23, 1177-1182.

Asymmetric and globular forms of acetylcholinesterase in mammals and birds.

Proc. Nati. Acad. Scn. USA Vol. 76, No. 6, pp. 2546-2550, June 1979 Biochemistry Asymmetric and globular forms of acetylcholinesterase in mammals an...
958KB Sizes 0 Downloads 0 Views