312

Biochimica et Biophysica Acta, 428 (1976) 312--320 © Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands

BBA 27859

CHEMICAL REACTIVITY OF LABILE S U L F U R OF I R O N - S U L F U R PROTEINS THE REACTION OF T R I P H E N Y L PHOSPHINE

TA KAS HI MANABE, KIYOSHI GODA and T O K U J I KIMURA *

Department of Chemistry, Wayne State University, Detroit, Mich. 48202 (U.S.A.) (Received September 15th, 1975}

Summary The reaction of triphenyl phosphine to iron-sulfur proteins from adrenal cortex mitochondria, spinach chloroplasts, and Clostridium p a s t e u r i a n u m was investigated. As ethanol concentrations in the reaction mixture increased, the rate of the reaction decreased. In the simultaneous presence of 1 M KC1 and 5 M urea, the reaction rate reached at maximum. Under these conditions the initial rates of the decolorization reaction by the phosphine were found to be 8.7, 0.88, and 1.8 nmol of ferredoxin per min at 25°C for adrenal, spinach, and clostridial ferredoxins, respectively. The kinetic curves for the reaction of the phosphine sulfide formation, the loss of labile sulfur, and the deterioriation of visible absorption showed a similar pattern with a comparable rate. During this reaction, the complete reduction of ferric ions present in ferredoxin was observed with a fast rate under either aerobic or anaerobic conditions. These results suggest that the iron atoms in ferredoxin are first reduced by the intramolecular reductants in the presence of triphenyl phosphine with the concomitant formation of S~-, which then reacts with triphenyl phosphine resulting in the formation of triphenyl phosphine sulfide.

Introduction

Ferredoxins, which are widely distributed in bacteria, plants, and animals, serve as a redox c o m p o n e n t for reductive carboxylation, nitrogen fixation, photosynthetic pyridine nucleotide reduction, and hydroxylation reactions. These proteins contain 2, 4 or 8 atoms of iron per molecule with equimolar amounts of labile sulfur atoms. Labile sulfur is liberated from the protein as * T o w h o m correspondence should be addressed. Abbreviation: S*, labile sulfur.

313 H2S upon acidification or denaturation of protein. It does not originate from the sulfur atom of cysteine, cystine, or methionine. We have previously reported that triphenyl phosphine, a nucleophile reacts with adrenal ferredoxin (adrenodixin), extracts its labile sulfur atoms quantitatively, and results in triphenyl phosphine sulfide as a final p r o d u c t [1]. This nucleophile is k n o w n to extract the sulfur atom (S °) of the persulfide bond (RSS-) and disulfide (S~-) in a variety of organic compounds, giving its sulfide, b u t the phosphine does not react to Na2S [2,3]. Therefore, it appeared at that time that persulfide bonds may occur in the iron-sulfur center of ferredoxins. However, recent studies including X-ray crystallography of bacterial ferredoxins [4,5] and the iron-sulfur cluster model complexes [6,7,8], strongly suggest that labile sulfur is a bridging ligand between two iron atoms. Thus, the formal oxidation state would be S 2-. If labile sulfur is indeed S 2-, a question how triphenyl phosphine reacts to labile sulfur must be answered. Under these circumstances we have decided to investigate the mechanism of reaction of triphenyl phosphine with iron-sulfur proteins from adrenal cortex mitochondria, spinach, and C l o s t r i d i u m p a s t e u r i a n u m . Materials and Methods Adrenal and spinach ferredoxins were prepared by following the methods of Kimura and Suzuki [9] and Tagawa and Arnon [ 1 0 ] , respectively. C l o s t r i d i u m p a s t e u r i a n u m ferredoxin was obtained from Sigma. The absorbance ratios of these proteins were: A4,4/A276 = 0.86 for adrenodoxin, A42o/A276 = 0.47, and A 39o/A 276 = 0.70 for clostridial ferredoxin. Ni(S2CC6Hs)2S2 and Zn(S~CC6Hs)S2 were synthesized by the m e t h o d of Fackler et al. [ 11]. Their elementary analysis were in good agreement with the theoretical values within experimental errors. Triphenyl phosphine oxide and its sulfide were synthesized by the reactions of triphenyl phosphine with acetic peracid and Sn, respectively. The products were identified b y melting points, infrared absorption spectra, and elementary analyses: for the oxide, m.p. = 156--7°C, infrared absorption maxima, 14.35, 13.82, 13.20, 10.00, 8.90, 8.40, 6.96 pm; for the sulfide, m.p. = 159--60°C, infrared absorption maxima, 14.45, 13.93, 13.21, 9.05 pm. Other chemicals of best quality were obtained from commercial sources. Spectrophotometric measurements were carried o u t b y an automatic recording spectrophotometer. Rapid reactions were followed by a Durrum-Gibson stopped-flow spectrophotometer. Radioactivity was measured by a Beckman liquid scintillation counter. The determination of labile sulfur was carried o u t b y the m e t h o d of Kimura and Suzuki [9]. Thin layer chromatography of [3H] triphenyl phosphine sulfide was carried o u t by the use of 99.7% hexane and 0.3% ethanol as a solvent. After the reaction with [3H] triphenyl phosphine was completed, 7 ml of 30% ethanol was added to 1.0 ml of the reaction mixture. The solution was placed on a small DEAE-cellulose column (0.5 × 2.0 cm). By washing with 10 ml of 30% ethanol, the unadsorbed portion was collected. After extracting triphenyl phosphine and its derivatives with ether (3-times), the ether extract was washed with water, dried over Na2SO4, and evaporated to dryness. The dried material was

314 dissolved in a small volume of ether, and t hen placed on the thin-layer chromatogram (Eastman-Kodak, No 6061). The RF-Values were f o u n d as 0.93, 0.71 and 0.11 f or triphenyl phosphine, its sulfide, and its oxide, respectively. T h r o u g h this manipulation, the recovery o f the total radioactivity was 44 + 5%. The molar ext i nc t i on coefficients used were: 9800 M-1 • cm -1 at 414 nm, 9600 M-1 • crn-1 at 420 nm, 30 800 M-1 . cm -~ at 390 nm for adrenal, spinach, and clostridial ferredoxins, respectively, and 11 300 M-~ • cm -1 for Fe2*-o p h e n a n t h r o l i n e c o m p l e x at 510 nm.

Results

Effects of ethanol Since triphenyl phosphine is n o t readily soluble in water, the reaction mixture has to include ethanol. We have, therefore, examined the effects of ethanol on the reaction of triphenyl phosphine with adrenodoxin. As the concentrations o f ethanol increased, the second order rate constants for the decolorization reaction decreased. Here, the c o n c e n t r a t i o n of ethanol below 25% could n o t be used, due t o the insolubility o f the phosphine. In the absence o f tri-

u A

i00 40 50 ~L 20 I

I

I

05

I B

100

=. "

40

50

_o 2 0

0.

o

"

0

I

I

I

I

i

!50

40 2O

%

,'o

8b Time

,~o

i~o

(minI

Fig. 1. R e l a t i o n s h i p e b e t w e e n d i s a p p e a r a n c e o f labile s u l f u r a n d f o r m a t i o n o f t r i p h e n y l p h o s p h i n e sulfide. r e a c t i o n m i x t u r e c o n t a i n e d 2 7 2 n m o l o f a d r e n a l f e r r e d o x i n in A, 3 2 0 n m o l o f s p i n a c h f e r r e d o x i n in B, o r 8 8 n m o l o f clostridial f e r r e d o x i n in C, 9 0 0 n m o l o f t r i p h e n y l p h o s p h i n e , 9 m m o l o f KCI, 4 5 m m o l o f u r e a , a n d 6 # t o o l o f p h o s p h a t e b u f f e r ( p H 7.4) in 9 . 0 m l o f 30% ( v / v ) e t h a n o l . T h e r e a c t i o n w a s c a r r i e d o u t at 25°C. e , labile s u l f u r c o n t e n t c a l c u l a t e d f r o m a b s o r b a n c e c h a n g e s at 4 1 4 , 4 2 0 , o r 3 9 0 n m for a d r e n a l , s p i n a c h a n d clostridial f e r r e d o x i n s , r e s p e c t i v e l y , o, labile s u l f u r c o n t e n t m e a s u r e d b y t h e m e t h y l e n e b l u e m e t h o d . A t r i p h e n y l p h o s p h i n e sulfide ( T P S ) f o r m e d . The

315

phenyl phosphine, the decolorization reaction was not observed at the concentrations of ethanol b e t w e e n 25% and 80%. The results indicate that when ethanol concentrations increased, the phosphine became less accessible towards the iron-sulfur chromophore. This effect of ethanol m a y be explained b y the increase in h y d r o p h o b i c interaction forces b y ethanol [ 1 2 ] , resulting in more c o m p a c t protein structures or polymerized forms. Effects o f urea and KCI In 1 M KC1 and 4 M urea, the iron-sulfur chromophore is stable under the conditions where polypeptide chain is partially unfolded [ 1 3 ] . We have investigated the effects of urea and KC1 on the reactivity of triphenyl phosphine with adrenal ferredoxin. In the absence of urea, the reactivity was not dramatically changed, whereas in the presence, the reactivity markedly increased as the concentrations of KC1 increased u p t o 1 M. In the presence of 1 M KC1, the reactivity increased as the urea concentrations increased u p t o 5 M. As clearly seen from these results, the presence of b o t h KC1 and urea is required for the m a x i m u m reactivity. In the presence of 1 M KC1 and 5 M urea, we have compared the reactivities with adrenal, spinach, and clostridial ferredoxins. The initial rate of the decolorization reaction b y the phosphine were found to be 8.7, 0.88 and 1.8 nmol per min at 25°C for adrenal, spinach, and clostridial ferredoxins, respectively. In the absence of KC1 and urea, the initial rates were 4.4, 0.81 and 0.39 nmol per rain, respectively.

!

i

i

0.300

0.200

l

_o

O. tO0 ~

n

00

_

I_

t

20 Time (rain)

30

Fig. 2. Effects of phospbines on the o-pbenanthroline reaction under aerobic c o n d i t i o n s . T h e r e a c t i o n mixture contained 55.2 nmol of adrenal ferredoxin, 150 nmol of phosphine, 450 nmol of o - p h e n a n t h r o line, and 6 #tool of phosphate buffer (pH 7.4) in 3.0 ml of 30% (v/v) ethanol. The r e a c t i o n w a s carried o u t at

25°C

(A), and

in

the presence of trlphenyl phosphine (o), triphenyl phosphine oxide (A), trlphenyl sulfide

in t h e a b s e n c e o f p h o s p h i n e

(o).

316

Comparison of the rates of reaction in terms of the decrease in visible absorbance, the loss of labile sulfur, and the formation of triphenyl phosphine sulfide As presented in Fig. 1, the kinetic curves for the reactions of the phosphine sulfide formation, labile sulfur loss, and decolorization are compared among adrenal (A), spinach (B), and clostridial (C) ferredoxins. It was clear in respective ferredoxins that the reaction rates of sulfide formation, labile sulfur loss and decolorization are roughly comparable. With respect to any of the three reaction rates, adrenodoxin had the fastest rate among other ferredoxins. There was no lag period for the formation of the phosphine sulfide, relative to the loss of labile sulfur or to the decrease in the visible absorbance. Wallace and Rabinowitz [14] reported that upon cyanolysis of bacterial ferredoxin by K~4CN, the formation of thio[14C] cyanide occurred much later than the release of H2S from the protein. Based upon these results, they concluded that the release of H~S occurs first, and then a slow reaction of H2S to KCN follows.

Effects of triphenyl phosphine on the formation of ferrous-o-phenanthroline complex Fig. 2 shows the effects of triphenyl phosphine on the formation of Fe2+-o phenanthroline complex from ferric ions present in adrenal ferredoxin. The reaction was carried o u t in the presence of 150 nmol of triphenyl phosphine under aerobic conditions (the upper curve). After 50 min of the reaction, all ferric ions were completely reduced to ferrous by the intramolecular reductants.

O. 300

0.200

E o

0.100

0 0

I0

20

30

40 50 Time (mln)

6o

Fig. 3. E f f e c t s o f t r i p h e n y l p h o s p h i n e o n the o - p h e n a n t h r o l i n e r e a c t i o n u n d e r a n a e r o b i c c o n d i t i o n s . T h e r e a c t i o n m i x t u r e c o n t a i n e d 5 5 . 2 n m o l o f adrenal f e r r e d o x i n , 4 5 0 n m o l o f o - p h e n a n t h r o l i n e , and 6 / ~ m o l o f p h o s p h a t e b u f f e r (pH 7 . 4 ) in 3 . 0 m l o f 3 0 % ( v / v ) e t h a n o l T h e r e a c t i o n w a s carried o u t at 2 5 ° C . T h e a m o u n t o f t r i p h e n y l p h o s p h i n e a d d e d w a s n o n e , 6 0 , 1 2 0 , and 2 4 0 n m o l in c u r v e s f r o m t h e b o t t o m t o the top, respectively.

317 The initial rate in the absence of the phosphine (6.4 • 10-7 M • min -1) was 1/7 of t h a t in the presence (4.7 • 10- 6 M • min-1). In the presence of triphenyl phosphine sulfide or oxide instead of the phosphine, the rate o f the reaction was n o t affected. Similar experiments unde r anaerobic conditions were carried out. The results are shown in Fig. 3. The initial rate of the f o r m a t i o n of Fe2÷-o-phenanthroline was 3.3 • 10-6M min -1 in the presence of 40 • 10-6M triphenyl phosphine, whereas the rate of the aerobic e x p e r i m e n t was 4.7 • 10-6M • min -1 in the presence of 50 • 10- 6 M phosphine. T he r efore, the rates of b o t h aerobic and anaerobic reactions are of a comparable o rder of magnitude, resulting in the c o m p l e t e r ed u cti on of ferric ions in the native prot ei n to ferrous ions.

Relationship between the absorbance loss at 414 nm and the disappearance o f labile sulfur under anaerobic conditions In order to k n ow how the loss of the visible absorbance correlates to the a m o u n t o f labile sulfur reacted with the phosphine, we have carried o u t the following experiments u n d e r anaerobic conditions. The reaction m i x t u r e containing a p p r o x i m a t e l y an equimolar a m o u n t of the phosphine to t h a t of labile sulfur in adrenal ferredoxin was treated at 37°C. Then, the remaining absorbance at 414 nm and residual a m o u n t of labile sulfur were determined. As shown in Table I, the e x t e n t of decolorization and labile sulfur disappearance are comparable in the repeated experiments.

02-consumption during the triphenyl phosphine reaction When one accepts the formal oxidation states o f iron and labile sulfur in the iron-sulfur cen ter as Fe 3÷ and S 2-, respectively, it would be predicted t hat Fe 3÷ are reduced by S 2- and the resulting Fe 2÷ will be reoxidized by 02 under aerobic conditions. We have measured the rates o f 02 upt ake by the triphenyl phosphine reaction in the presence and absence of catalase. The results are shown in Table II. From these data a reaction p r o d u c t is H~O2.

Rates o f reaction o f triphenyl phosphine with S°-containing model complexes Using a stopped-flow s p e c t r o p h o t o m e t e r with a dead-time o f 2 ms, we have studied the rate o f reaction of triphenyl phosphine with k n o w n complexes with S °. We have synthesized Ni(S*S2CC6Hs)2 and Zn(S*S2CC6Hs)2 as r e p o r t e d

TABLE I RELATIONSHIP BETWEEN THE LOSS OF ABSORBANCE SULFUR UNDER ANAEROBIC CONDITIONS

AND THE DISAPPEARANCE

OF LABILE

The reaction mixture contained 2.5 mM phosphate buffer (pH 7.4) and 25% ethanol. Expt. No.

I II III

Reaction mixture

Temp. (o C)

Adrenodoxin (M X 1 0 4 )

Phosphine (M X 1 0 4 )

1.63 1.47 1.41

2.93 2.93 2.83

37 37 30

Time (h)

19 17.5 17.5

P e r c e n t loss in Absorbance

Labile sulfur

69.1 61.1 45.1

61.6 68.6 52.8

318 T A B L E II O X Y G E N C O N S U M P T I O N BY T H E T R I P H E N Y L P H O S P H I N E R E A C T I O N T h e o x y g e n u p t a k e w a s m e a s u r e d b y a r o t a t i n g e l e c t r o d e ( G i l s o n - K M ) at 3 0 ° C . T h e t o t a l v o l u m e o f t h e reaction m i x t u r e was 1.70 ml. Medium

Additions

3 5 % e t h a n o l , 3.5 M u r e a , 0.7 M K C I in 0.01 M p h o s p h a t e b u f f e r ( p H 7.47

t r i p h e n y l p h o s p h i n e (4 t t m o l ) adrenodoxin (0.2 ttmol) t r i p h e n y l p h o s p h i n e (4 t t m o l ) + a d r e n o d o x i n (0.2 ttmol) t r i p h e n y l p h o s p h i n e (4 # m o l ) + a d r e n o d o x i n (0.2 ttmol) ÷ catalase (20 #g) t r i p h e n y l p h o s p h i n e (2 Drool) + a d r c n o d o x i n (0.2 p m o l ) t r i p h e n y I p h o s p h i n e (2 jRmol) + a d r e n o d o x i n (0.2 p m o l ) + catalase (20 pg)

2 0 % e t h a n o l in 0 . 0 1 M p h o s p h a t e b u f f e r ( p H 7.47

02 -uptake nmoles/min

a d r e n o d o x i n ( 0 . 4 ~tmol) triphenyl phosphine (4/~mol) + a d r e n o d o x i n (0.4 # m o l ) t r i p h e n y l p h o s p h i n e (4 p m o l ) + a d r e n o d o x i n (0.4 p m o l ) + catalase (20 ~g)

0 4.2 61.2

23.9 43.4

18.7 2.3 5.7

3.6

previously [ 1 ] . Upon the reaction of triphenyl phosphine, the visible absorbance changed. The second order rate constants were calculated to be 2.7 • 104 and 7.9 • l 0 T M"1 • min -1 at 25°C for the respective Ni and Zn complexes. An analogous complex, (CH3C6H4CS2)Fe(S*S2C6H4CH3), has been det erm i ned by

TABLE

Ill

KINETIC RESULTS OF THE REACTIONS DOXINS WITH TRIPHENYLPHOSPHINE

OF

Ni(dtb)2S2, Ni(dtb)2S, Zn(dtb)2S2 A N D

dtb: $ 2 C C 6 H 5 . Compounds N i ( d t b ( 2 S 2, 2 . 5 • 1 0 - 5 M P h 3 P , 5 . 0 " 1 0 -4 M N i ( d t b ) 2 S , 8 . 3 • 10 -5 M P h 3 P , 1.7 • 10 - 3 M N i ( d t b ) 2 , 8 . 3 • 10 -5 M P h 3 P , 1.7 1 0 - 3 M Z n ( d t b ) 2 S 2, 2 . 0 . 10 - 6 M Ph3P, 4.0 10 -6 M Z n ( d t b ) 2 , 2 . 0 . 10 - 6 M Ph3P, 4.0 ' 10 -6 M A d r e n o d o x i n , 6.0 • 10 -5 M P h 3 P , 1 . 0 • 10 - 4 M S p i n a c h f e r r e d o x i n , 7.1 . 10 -5 M Ph3P, 1.0 • 10 -4 M C ] o s t r i d i a l f e r r e d o x i n , 7 . 0 - 10 -5 M P h 3 P , 1.0 • 10 -4 M •



Temp. (Oc)

h ( M -! • s-I)

25

450

1.2

25

--

1.2

25

not reacted

25

1.3 • 106

25

not reacted

25

--

22.0

25

--

2.0

25

--

1.5

--

FERRE-

319 X-ray crystallography [15]. The labile sulfur of this complex was also extracted by triphenyl phosphine. Being in contrast to this, Na2S, (RS)2metal(SR)2, and (o-phenanthroline)2-Fe(OH)2Fe(o-phenanthroline)2 did not react with triphenyl phosphine. These results are summarized in Table III. Discussion The chemical nature of labile sulfur has been long subjected to debate. Recent studies by X-ray crystallography revealed that the labile sulfur of Fe4S*4 clusters in bacterial ferredoxins is a bridging ligand between two iron atoms [4,5]. In Micrococcus aerogenes ferredoxin, the interatomic distance between the two labile sulfur atoms was estimated as 3.53 A + 0.10 A by a least-square refinement m e t h o d [4]. On the other hand, Holm and his group [6,8] and Dahl and his colleagues [7] have successfully synthesized Fe4S*4 and Fe2S*2 cluster models of ferredoxins. The X-ray crystallographic data of [FeS(SCH2)2(C6H4)] ::- suggested that as judged from the interatomic distance of the two labile sulfur atoms (3.498 A), the labile sulfur has a formal valence of S 2-. excluding perthiocysteinyl group, or persulfide. In Na2S:, the interatomic distance is 2.15 A. As well, [Fe4(NO)4(p3-S)4] °, and [Fe4S4(SCH2(C6Hs)4] 2- had the distance of 3.507 )k, and 3.586 A, respectively. This bridging model is consistent with the implication that the value of the oxidation stoichiometry of 2Fe-2S* center is about 8 [16,17]. We have found in this study that the triphenyl phosphine reacts with labile sulfur under either aerobic or anaerobic conditions. Concomitantly, all ferric ions in ferredoxin are reduced to ferrous ions. From the kinetic studies, the release of H2S from the protein could not be detected prior to the formation of the phosphine sulfide. From the results with the model complexes, the rate of the phosphine reaction with ferredoxin appears to be comparable to that of Ni(S3CC2Hs):. All of these results are consistent with the persulfide hypothesis, except the oxidation stoichiometry of the iron-sulfur center with a value of 8. Using the molecular orbital theory, Loew and Steinberg [18,19] calculated that total configuration energies of neutral Fe2S*2 cluster. As a lowest energy conformer, both of the iron atoms and ferric, and the labile sulfur is not S 2-, but S~- or HS-. Yet, our laser Raman scattering measurements did not detect a disulfide bond in adrenal ferredoxin [20]. As pointed out by Orme-Johnson [21], we must admit "softness" of chemical approaches aiming the determination of the formal valence of labile sulfur. Until the highly resolved X-ray crystallographic data become available, the formal valence remains uncertain. Yet, assuming the oxidation state of labile sulfur as S 2-, our results can be interpreted as the following reaction sequence: Ph3P

(RS-)4(Fe3+S 2-)2 lO_6 M. m i l l 3 0 2 + Ph3P

1 0 - 8 M • rain-I

-1

, 2 Fe2+ +S2 2- + 4 R S -

"'"

2 Fe 2÷ + 2 Ph3P = S + 2 RS-SR + 3 022-...

(1) (2)

The above stated circumstancial evidence together with the fact that bacterial

320 ferredoxin with bridging sulfur atoms reacts with the phosphine would support "~ the reaction sequence via S~- species.

Acknowledgement This study was supported by a Research Grant from the National Institutes of Health (AM-12713).

References 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

K i m u r a , T., Nagata, Y. a n d Tsurugi, J. ( 1 9 7 1 ) J. Biol. Chem. 2 4 6 , 5 1 4 0 - - 4 6 Tsurugi, J., N a k a b a y a s h i , T. a n d Ishihara, T. ( 1 9 6 5 ) J. Org. Chem. 30, 2 7 0 7 - - 1 0 Tsurugi, J., Hori, T.~ N a k a b a y a s h i , T. a n d K a w a m u r a , S. ( 1 9 6 8 ) J. Org. Chem. 33, 4 1 3 3 - - 3 5 A d m a n , E.T., Sieker, L.C. a n d Jensen, L.H. ( 1 9 7 3 ) J. Biol. Chem. 2 4 8 , 3 9 8 7 - - 9 6 Carter, Jr., C.W., K r a u t , J., Freer, S.T., Alden, R.A., Sieker, L.C., A d m a n , E. a n d Jensen, L.H. ( 1 9 7 2 ) Proc. Natl. Acad. Sci. U.S. 6 9 , 3 5 2 6 - - 2 9 H e r s k o w i t z , T., Averill, B.A., H o l m , R.H., Ibers, J.A., Phillips, W.D. a n d Weiher, J.F. ( 1 9 7 2 ) Proc. Natl. Acad. Sci. U.S. 6 9 , 2 4 3 7 - - 4 1 Gall~ R.S., Chu, C.T-W. a n d Dahl, L. F. ( 1 9 7 4 ) J. Am. Chem. Soc. 9 6 , 4 0 1 9 - - 2 3 Mayerle, J.J., Frankel, R.B., H o l m , R.H., Ibers, J.A., Phillips, W.D. a n d Weiher, J.F. ( 1 9 7 3 ) Proc. Natl. Acad. Sci. U.S. 70, 2 4 2 9 - - 3 3 K i m u r a , T. a n d Suzuki, K. ( 1 9 6 7 ) J. Biol. Chem. 2 4 2 , 4 8 5 - - 9 1 T a g a w a , K. a n d A r n o n , D A ( 1 9 6 2 ) Nature 1 9 5 , 5 3 7 - - 4 3 Fackler, J.P. Jr., F e t c h i n , J.A. a n d Fries, D.C. ( 1 9 7 2 ) J. Am. Chem. Soc. 94, 7 3 2 3 - - 3 3 E p a n d , R.M. a n d S c h e r a g a , H.A. ( 1 9 6 8 ) B i o c h e m i s t r y 7, 2 8 6 4 - - 7 2 Petering, D.H. a n d Palmer, G. ( 1 9 7 0 ) Arch. Biochem. Biophys. 1 4 1 , 4 5 6 - - 6 4 Wallace, E.F. a n d R a b i n o w i t z , J.C. ( 1 9 7 1 ) Arch. B i o c h e m . Biophys. 1 4 3 , 4 0 0 - - 9 C o u c o u v a n i s , D. a n d L i p p a r d , S.J. ( 1 9 6 8 ) J. Am. Chem. Soc. 9 0 , 3 2 8 1 - - 2 Petering, D.H., Fee, J.A. a n d Palmer, G. ( 1 9 7 1 ) J. Biol. Chem. 2 4 6 , 6 4 3 - - 5 3 Manabe, T. a n d K i m u r a , T. ( 1 9 7 4 ) FEBS L e t t . 4 7 , 1 1 3 - - 1 6 L o e w , G.H. a n d Steinberg, D.A. ( 1 9 7 1 ) T h e o r e t . Chim. A c t a 2 3 , 2 3 9 - - 5 8 L o e w , G.H. a n d S t e i n b e r g , D.A. ( 1 9 7 2 ) T h e o r e t . Chim. A c t a 2 6 , 1 0 7 - - 3 0 Tang, S-P.W., Spiro, T.G., Mukai, K. a n d K i m u r a , T. ( 1 9 7 3 ) B i o c h e m . Biophys. Res. C o m m u n . 53, 869--74 O r m e - J o h n s o n , W.H. ( 1 9 7 3 ) A n n u . Rev. Biochem. 42, 1 5 9 - - 2 0 4

Chemical reactivity of labile sulfur of iron-sulfur proteins. The reaction of triphenyl phosphine.

The reaction of triphenyl phosphine to iron-sulfur proteins from adrenal cortex mitochondria, spinach chloroplasts, and Clostridium pasteurianum was i...
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