Gene, 119 (1992) 123-126 0 1992 Elsevier Science

GENE

Publishers

B.V. All rights reserved.

123

0378-l 119/92/$05.00

06652

Isolation and complete sequence synthase II in Lactobacillus casei

of the

purL

gene

encoding

FGAM

(Purine operon; purC, pure; purF)

Gu a*, Duane W. Martindale”

Zheng-Ming ‘I Depurtment Qkbec, Received

and Byong H. Leeb

qf Microbiology, and b Department of’ Food Science and Agricultural Chemistry, McGill University. Macdonald Campus, Ste. Anne de Bellevue,

Canada. Tel. (514) 398-7979 by R.E. Yasbin:

24 February

1992; Revised/Accepted:

28 April/4

May 1992;

Received at publishers: 8 June 1992

SUMMARY

The purL gene from Lactobacillus casei, encoding phosphoribosylformylglycinamidine synthase II involved in the de novo synthesis of purines, was cloned and sequenced. The putative purL product of 741 amino acids (M, of 79 575) shows 25 y0 and 53”/b identity to the homologous enzymes from Escherichia coli and Bacillus subtilis, respectively. In addition, partial sequences of two other pur genes (purQ and purF) and a possible third gene (purC) were obtained. All these genes are organized in an operon similar to that of B. subtilis. In contrast, the corresponding genes from E. coli and Salmonella t~~phimuriumare scattered through the genome.

INTRODUCTION

The de novo purine nucleotide biosynthetic pathway includes ten enzymatic steps leading from fi-phosphoribosyl1-pyrophosphate to IMP. One of these steps, the conversion of phosphoribosylformylglycinamide (FGAR) to FGAM, is catalyzed by FGAM synthase. In E. coli

Correspondence 21111 Lakeshore

to:

Dr. D. Martindale,

Department

of Microbiology,

Rd., Ste. Anne de Bellevue, Quebec,

ada. Tel. (514) 3987886; Fax (514) 398-7990. * Present address: Institute of Parasitology, McGill

H9X

ICO, Can-

University,

Mac-

donald Campus, 21 111 Lakeshore Rd., Ste. Anne de Bellevue, Quebec H9X lC0, Canada. Tel. (514) 398-7999. Abbreviations: aa, amino phosphoribosylformylglycinamidine;

acid(s); kb,

bp, base kilobase

pair(s); FGAM, or 1000 bp; L.,

Lactobucillus; nt, nucleotide(s); ORF, open reading frame; oligo, oligodeoxyribonucIeotide; purC, gene encoding SAICAR synthase; p&r, gene encoding

~idophosphoribosyItrausfcrase;

purl,, gene encoding

synthase II; prtre, gene encoding FGAM phospho~bosyi~inoimidazolesuccinocarbox~ide.

synthase

I;

FGAM SAICAR,

(Schendel et al., 19X9),S. typhimurium (French et al., 1963) and chicken liver (Mizobuchi and Buchanan, 1968) this enzyme is a monomer (M, of approx. 135 000) encoded by purL. The FGAM synthase from B. subtilis is composed of two polypeptides (FGAM synthase I, M, of 24755, and FGAM synthease II, M, of 80300) encoded by the pure and purL genes, respectively (Ebbole and Zalkin, 1987). FGAM synthase I contains the glut~ine amide transfer domain of FGAM synthase, while FGAM synthase II contains the aminator domain (Ebbole and Zaikin, 1987). Genes encoding most of the purine biosynthetic enzymes have been mapped in S. typhimurium and E. coli (Bachmann, 1990; Gots et al., 1977; Sanderson and Hartman, 1978) and the majority of the E. coli genes have been cloned and sequenced (Ebbole and Zalkin, 1987; Schendel et al., 1989; Smith and Daum, 1986; Tso et al., 1982). In both organisms these genes are dispersed on the chromosome. In contrast, the homologous genes of B. subtilis are clustered in an operon (Ebbole and Zalkin, 1987). In this paper we report on cloning L. casei pur genes, the nt sequence of the purL gene encoding FGAM synthase II and the

124

B.

ORF

subtilis

purD

1 kb L

-

casei

pLLo1435

+

pLSPZ0

B XS I ,r

PP \I 4+ ii:: // ii : f j: -

s-’

pLPE7 Fig. 1. The organization designated

according

by boxes. Genomic AccI; B, BarnHI; sequencing.

of the purine biosynthetic

to E. coli nomenclature DNA fragments

E, EcoRI;

Plasmids

pIBI30

carried

H, HindHI; and pIBI31

A

H

I

c

genes of L. casei and B. subtilis (Ebbole and Zalkin,

(Bachmann, in the original

P, &I;

B 1 / ;: : !: :;

1990). Coding

regions

clone (pLLG1435)

S, SphI; X, XbaI. Arrows

(International

Biotechnologies,

1987). Genes have rightward

and ORF of unknown

and in two subclones show regions

of cloned

I

function

(pL-SP20

(Ebbole

and pL-PE7)

Standard

methods

and are

1987) are shown

are indicated

DNA which were sequenced

Inc.) were used as vectors.

orientation

and Zalkin,

by lines. A,

and the direction

were employed

of

for DNA

manipulations.

partial genes.

sequences

EXPERIMENTAL

of the pure,

purF and possibly

purC

AND DISCUSSION

(a) The purL gene and its product The original clone (pLLG1435; Fig. 1) was isolated from an L. casei genomic DNA library during an attempt to clone an unrelated gene. An oligo probe, corresponding to a portion of the L. casei caprylate-esterase enzyme (Gu, 1992) was found to hybridize to the SphI-PstI fragment within pLLG1435. This fragment was subsequently determined to contain the purL gene, not the caprylate-esteraseencoding gene. The purL gene was identified by the similarity of its deduced aa sequence to the B. subtilis FGAM synthase II (Ebbole and Zalkin, 1987). Fig. 2 shows the nt and deduced aa sequences of a 2925 bp SphI-EcoRI fragment (Fig. 1) from L. casei genomic DNA containing the complete purL gene, the 3’ end of the pure gene and the 5’ end of the purF gene. The L. casei purL coding region is 2223 bp, encodes a putative polypeptide of 741 aa with a deduced A4, of 79575 as compared to the B. subtilis protein of 742 aa with an A4, of 80300. The alignment of the FGAM synthase II polypeptides of L. casei, B. subtilis (Ebbole and Zalkin, 1987) and the homologous domain of E. coli FGAM synthase (Schendel et al., 1989) (Fig. 3) showed that the L. casei enzyme shares 53% of its aa (395 out of 741 aa) with the B. subtilis enzyme, and 25 y0 (182 out of 74 1 aa) with the E. coZiFGAM synthase II domain region. When regions where the three proteins overlap were examined, the E. coli polypeptide was equally similar to the L. casei (25 y0; 179 out of 730 aa) and B. subtilis enzymes (25% ; 183 out of 730 aa).

(b) Other pur genes are adjacent to purL The sequencing data revealed that upstream from the purL gene is the pure gene, and downstream, the purF gene was found (Figs. 1, 2 and 4). The L. caseipurL gene overlaps with 20 bp of the pure gene and with 28 bp of the purF gene (see Fig. 2); these overlaps in B. subtilis are 17 bp and 25 bp, respectively (Ebbole and Zalkin, 1987). The putative C-terminal end of the L. caseipurQ gene product shares 32 out of 54 aa (59%) with the equivalent region of the B. subtilisFGAM synthase I (Ebbole and Zalkin, 1987). The putative N-terminal end of the L. casei purF gene product shares 94 out of 193 aa (49%) with the same region of the B. subtilis amidophosphoribosyltransferase (Makaroff et al., 1983) (Fig. 4). The two ends of the 8-kb genomic DNA fragment cloned into pLLG1435 (Fig. 1) were also sequenced. The sequence of the end upstream from purL appears to contain a small portion of the 5’ end of the purC gene (63 bp) at approximately the same position as the purC gene in B. subtilis (Fig. 1) (Ebbole and Zalkin, 1987). However, since the deduced N-terminal aa sequence of the putative L. casei purC gene product (SAICAR synthase) shares only 8 out of 21 aa (38%) with the same region of the B. subtilis enzyme (Fig. 4) this assignment should be considered tentative until further work is done. The sequence of the downstream end of pLLG1435 was not found to be homologous to any sequences in the databases.

REFERENCES Bachmann,

B.J.: Linkage map of Escherichia

coli K-12, edition

8. Micro-

biol. Rev. 54 (1990) 130-197. Chen, E.Y. and Seeburg, P.H.: Supercoil sequencing: A fast and simple method for sequencing plasmid DNA. DNA 4 (1985) 165-170.

12.5

1 GCATGCACGiTATTGCCGGiGTGACCAAT~AGACTGGTA~TGTG~AGG~ATGATGCCC~ATCCGGAAC~GGCTG~GA~GCACTGCTG~GCGGTACGGiTGGCTTGGGtGTATTCCAA~ PHPERAVEALLGGTDGLGVFQ purQ-...M H D I A G V T N E T G N V L G M H 121 CGCTGATTAiCCAAACGGAiGGAGCCG~TACGTGGTGtACGTiGAGAiGAGCCCCGA~GCTATTGCAiCCCAGAAAC~~ATTTAGA~CTTGGGCTGiCAGAGGCTGiATATGATCGi SLINQTEGADVRGAR. IATQKPYLDLGLTEAEYDR 1 purLM Y V V H V E M 5 P E A 241 TTTGCAGAAtTAATCGGCCiTCAGCCAAAtGATACCGAGiTCGGGTTAGtTAGCGGTAT~TGGAGCGAAtACTGCGCTTiCAAATATAGtAAGCCGGTA~TACGCCAATiTTGGACCAAi 32 F A E L I G H Q P ND T E I G LA 5 GM W S E H C A Y KY 5 K P V L R Q

F

W

T

K

361 AATGAGCGCirTGTTAATGGi;GCCAGGTGAiGGTGCTGGC~TGATTGATAiCGGCGAAGG~AAAGCAGTGiiTCTTCAAAGtCGAAAGTCAiAATCATCCCiCGGCAGTTGiACCTTATGA~ 72 N E R VLM G P G E GA G V ID I G E G K A V V F K A E 5 H N H P S A V

E

P

Y

E

S

F

A.S

481 112

GGCGCAGCAiCAGGTGTGG~CGGCATAATiCGCGACAT~TCTCAA~G~TGCCAAGCC~GTTGCGATGiTGGACTCGCiAGC~TTGGtGACATTGAA,CAGCCACATAtCCAACATTT~ GAATGVGGIIRDIFSIGAKPVAMLDSLAFGDIEQPHTQHL

681 GTTGATCGGiTTGTCGCGG~GA~GGCGGiTATGGCAAT~CAATTGGCA~TCCGACAGTiGGCGGCGAAiCAAACTTTGiCGGGAGCTAiACCCGAAATtCGCTGGTCAiTGCCATGTGt 152 VDRIVAGIGGYGNAIGIPTVGGETNFDGSYTRNPLVNAHC 721 GTTGGCATCiTGGACAAAGiTCAAATTCA~AAAGGTAAA~CTGCTGGTG~TGGCAATGCiTTGATTTAT~TCGGGGCCAiAACAGGGCGiGATGGTATTiACGGTGCGAi.CTTTGC~Ci 192 V G IM D K D Q I QK G K A A G V G N A L I Y V GA K T G R D G IN GA 841 GGGGATTTTTCTGACGAAGiAGCAGCCGATCGCTCGGCGi;TTCAAGTTG~CGATCCCTTtATGGAAAAGtTGTTGATGG~TGC~GTCTtGAAATTACCtGGCATCATCiGGAGGCGC~ 232 GDFSDEEAADRSAVQVGDPFMEKLLMDACLEITGHHQEAL 961 G~GGTATTtAAGATATGGtTGCAGCTGG~~GGTATCGiGATGGCTGGiAAGGCTAACiGCGGGATGG~G~AGATCTtGdTCTGATT~CGCAGCGTG~AGCCGAAAT~ 272 VGIQDMGAAGLVSSSVEMAGKANSGMVLDLDLIPQREAEM 1881 ACGCCGTTT~AAA~ATGT~GTCTGAGTC~CAGGAACGGiTGCTGCTAT~CGTTCGGGCtGGCTTTGAGtAAGAAGTTTiGGCTGTTTTtGCCGATTATtATTTGGATGiGGCGATTGTi 312 TPFEIMLSESQERMLLCVRAGFEQEVLAVFADYDLDAAIV 12Bl 352 1321 AAACGACTGiCCCAACCGGtTGCGGATT~GACCCTATCiTCACTGATCiGGTGCAAATiTGGACGGACiTGATGGCGAiGCCGACGA~GCTGACAAGiCATCTTTGTiCAAGCG~A~ 392 KRLAQPAADFDPIITDPVQIWTDMMAMPTIADKSSLYKRY 1441 432

GATGCGCAGi;TGCAAACTAiTACCGTCGTtTTGCCAGGCiGTGATGCAGtCGTGATTCG~ATTCGCGGT~CTCACCGAGtACTGGCGAT~ACCACCGATiGTAAGGACGiTACTTGTAT~ DAQVQTNTVVLPGSDAAVIRIRGTHRALAMTTDSKDVTCI

1561 TTGATCGCAGGTGGGTGCGGCAATGAGTGiTGGCTGAAAtGTGCGCGCAiTTTGGTTGCtAGCGGGGCGirAACCGCTTGGGATCACCGAiTGTCTCAATiTTGGCGACCtAACTAAGCCi 472 LIAGGCGNECWLKRARNLVASGAEPLGITDCLNFGDPTKP 1681 GAGGCCTTCiACGAACTGGtTGAGGCGGC~AAGGGAATCi~GCGGCTA~CAAAGCCTTiAACGCCCCA~TTA~TCAG~AAATGTGTC~CTGTATAAC~AAACGAATG~TGAGGCGAT~ 512 EAFYELAEAAKGIIAATKAFNAPVISGNVSLYNETNGEAI 1801 TATCCAACCtCAATGATTGi;CATGGTTGGtTTGATTGAG~ATTTGAGCAtGATCACCAC~GCGGCTTTC~AGCAAGCAGiTGATCTGAriTATCTGGTG~GGGAAACTC~TGGTGATTTi 552 YPTPHIGMVGLIEDLSTITTAAFKQADDLIYLVGETHGDF

1921 AACGGCAGC~AACTGCAGAiGCTGCAAACiGGAGAAGTCiCTGGCAAGCiGTTCGATTTiGATTTAGAG~CTGAAAAGCiGCATCAGCAtTTTGTTTG~AGGCCATTCtCGAGCATCTi 592 NGSELQKLQTGEVTGKLFDFDLEAEKQHQHFVLKAIREHL 2041 ATTACTGCAGCGCACGArriAGCGATGGiGGGTTGTTGiGTCACATTGtCGACTGCTTtGGGATTTTCC 632 ITAAHDLSDGGLLVALAEMGFDAQLGAQINVTLPTAWGFS 2161 GAGACGCAAGGCCGCTTCTiGCTCACCGTGTCCCCTGAAiTCAGGCAGtATTTGAAGCiTTCCATGGCtCGGCCCAAT~GATTGGTCG~GTTCAGGCCtCACCAGAATiTGAAGTCACA 672 ETQGRFLLTVSPENQAAFEALHGPAQLIGRVQAPPEFEVT 2281 712 1

purF-M

P

H

E

P-R

L

K

M

K

N

A

G

F

R

C

W

G

2481 ._ ATCCTAATG~CGCCAGCAT~ACGCAT~TTGGGTT~CACA~ACTACAGCA~CGCGGTCAA~AAGG~G~~G~TATTGTTGG~CTGACCAAA~ACGGGATGC~GCGGCA~A~GGGTTGGGG~ lYNPNAASITHLGLHTLQHRGQEGAGIVGLTKDGMRRHYGLG

2521 TACTGAGCGiAGTTTTCAC~AATACCGATtAATTGACGCtnTTAATCGGiCGGGCCACGiGCGCTACTC~ACAGCAGGGGGdCGCGTGCiGGAAAACATiCAGCCGTTGt 59LLSEVFTNTDQLTPLIGRAALGHVRYST,AGGRVLENIQPL

2641 TTTTCCGGTirTCGGATGAiGCCArrGCCiTGGCGCATAiTGGCAATCTGACCAATGCGiTCAGTTTGCGGCGGCAGTTGGAAGATCAAGGCGCAATTTTTCAGTCCACtTCCGATACGG 99LFRFSDEAIALAHNGNLTNAISLRRQLEDQGAIFQSTSDT 2761 AAGTTTTGAiGCATTTAAT~CGACGGCAA~TTGGCCAGCtTTGGCTGACiCAGTTGAAG~CCGCTTTAA~TGAAGTTCAiGGTGGTTTT~CGTTTGTCT~ACTGACGGAiCATGGT~Ai 139EVLMHLIRRQVGQPWLTQLKTALNEVHGGFAFVLLTEHGL

2881 ATGCCGCAGiTGATCCGCAiGGCTTTCGGtCGATGGTTGiCGGGG 179 Y

Fig. 2. Nucleotide

A

A

V

for sequencing

Plasmids

indicated

Ebbole,

G

aa sequence

were prepared

using the MacVector

using the FASTA

D.J. and Zalkin,

nucleotide

synthesis.

T.C., Dawid,

reactive

R

P

M

V

V

sulthydryl

G...

2925 193

of the purL gene encoding (Chen

FGAM

and Seeburg,

by an alkaline lysis procedure

in Fig. 1 as well as a series of plasmids

synthase

II. The ORF of purL begins at 148 (ATG). The 3’ end sequence

3.5 DNA

program

H.: Cloning

(Pearson

and aa sequence and Lipman,

and characterization

(Hattori

analysis

program

1988). GenBank

of a 12-gene

J. Biol. Chem. 262 (1987) 8274-8287. group

5’-

method

1986) and sequenced

(Henikoff,

1984) created

using a synthesized

accession

(Sanger

are under-

et al., 1977). Double-stranded

using T7 DNA polymerase from plasmids

primer (University

(IBI). A scan of the protein

databanks

pL-SP20

of Calgary). (SwissProt,

(Pharmacia).

and pL-PE7

were

Sequence

data

Version

19) was

diphosphate).

J. Biol.

No. M85265.

phosphate:

L-glutamine

amido-ligase

(adenosine

Chem. 238 (1963) 2171-2177. Gots,

J.M.: Azaserine-

of 2-formamido-N-ribosylacetamide

and Sakaki,

deletions

was sequenced

nine enzymes for de novo purine

I.B., Day, R.A. and Buchanan,

from pm-L, shares 28 bp with purL. Start codons

1985) of the chain-termination

with increasing

the two PstI sites in pLLG1435

cluster from Bacillus subrilis encoding French,

F

20 bp of purL. The 5’ end of the purF gene, found downstream

The small region between

were analyzed performed

H

was done using a modification

templates sequenced.

P

and deduced

of the pure gene overlaps lined. Sequencing

D

J.S.,

Benson,

C.E., Jochimsen,

models and regulatory CIBA Found.

elements

B. and Koduri, in the control

Symp. 48 (1977) 23-41.

K.R.:

Microbial

of purine metabolism.

126 Lc Bs EC

L 1 151

---

50 49 211

IEXMFA l

_*- c%iimu&................YDIG.... m................m QrsmEHCRHKIP t

_Lc B8 EC

90 89 271

La Em EC

134 133 331

Lc Bs EC

174 173 391

Lc Bs EC

282 279 508

_

*t**

_*_-

wf’ IQ....

***t*

l

--*_

** --

--

l

-

__*

--

t.

.* t

IIRD..IFBI &PvA

_*_,_

--

342 339 568

_...._**_*_**

.L

-*_

*

_--

t

t*

-

L.c 506 Ba 505 EC 741

Fig. 4. Sequence comparisons

QmF-.~~PPKaK...~..QcnALm-

QGA?SE.

and purF prod-

of the putative purC.purQ

ucts from L. cosei (Lc) with those from B. subtilis (Bs). Data for B. subtilis

.DMPILFI~

are from Ebbole

and Zalkin

(1987). Colons

denote

similar aa (A,G/S,T/D,E/N,Q/H,K,R/I,L,M,V/F,Y,W); end of polypeptide.

t

A.--_‘_

t t

programs,

--.ltW3&-1YIMWRldPK.

-*-

Sequences

University

Gu, Z.M.: Cloning

(GCG

of Wisconsin,

Madison,

and Sequencing

WI).

Cloning

of the Caprylate-Esterase

McGill University, * AL........... AL........... AIWVIDNU?F AVl'l'~V~I~IWW

-

Her&off,

templates.

l

*

Makaroff,

t

Canada,

C.A., Zalkin,

digestion

H., Switzer,

casei and

M.Sc.

Thesis,

method using denatured

152 (1986) 232-238. with exonuclease

for DNA sequencing.

the Bacillus subtilis glutamine

Gene.

1992.

sequencing

Anal. Biochem.

S.: Unidirectional

geted breakpoints - _=-

Montreal,

M. and Sakaki, Y.: Dideoxy

plasmid

-_'_

of the Phosphoribosylformylglycina-

II Gene from Laccobacillus casei subsp.

Synthase

Attempted

tt

denote

were aligned using the Gap program

.RIAQP . . . ..AK

t

chemically

asterisks

--

DKYllLWiWm. FSWAPYAWOPP

"I -. . . .om...-mYPrP... . . ..(~E...~Yrn... mmvRAmmm

228

l

398 397 623

458 457 681

I

--mMNP3u3

Hattori, Lc Be EC

I

__=*___*

midine Ic B8 EC

:

AY

enzyme

Lc Be EC

III III :Ill:: ERAVDgLL0sAcG~PQSI*

l

_"_'

..EVaFD88PEXIN......PLmlR IMLuwIrnR.

QASF-.I..

? bWDIP=~~~SLl~GM* : IIIII II IIIIIIIIIIIIII: “SDImK

BB 175

lKmaiclQIpIux3...

.. .... PLL%lAmmaIMxDQI

..-

l

(3’endl

LC

EIrn..WSW3RRPIA

* * _= -=ML.....~~ev..DRIvMI..........~I~... VL.....~PRVKYLF..~I..........

* 226 225 450

l

. . . . . . .. . . . . ..maAwFKI YFmw YDFmEPmAIs

*

Lc Ba EC

DWC (5’endl

l. _*--

l

-

ARmrnP ttt*

Lc BE EC

*

----

I4YbnmwPpm...IQlfQmti l.z¶uma~KBsI...~QIR9

III creates

tar-

Gene 28 (1984) 351-359.

R.L. and Vollmer, S.J.: Cloning of

phosphoribosylpyrophosphate

amido-

gene in Escherichia coli. J. Biol. Chem. 258 (1983) 10586-

transferase 10593.

Lc Bs EC

556 555 801

Mizobuchi, VIQ4WUEQBFRPW~YGKAFQIDLVJ VIEW tt

Lc BS EC

616 615 858

Lc Bs EC

657 657 918

.-!&,Ji&kIT....d~ .vmFvQ..

*t* .

t . . . . . . . . . . . ..FDW.L . . . . . . . . . . .r4ITENL

. . P..

l

ii‘wiG%Le.. -

C. -VI

---

- --...-FFls?mQPoPnoLlaWMAeP.

. .. .

of the FGAM

synthase

II aa sequences

from differ-

Lc, L. casei; Bs, B. subtilis (Ebbole and Zalkin,

and one of the other proteins;

protein does not have a corresponding aligned using the Pileup program sin, Madison,

WI).

Sanderson,

1987); EC,

a full stop denotes

aa at this position.

(GCG programs,

D.J.: Improved

Proc. Natl. Acad.

XXX.

K.E.

and

Hartman,

P.E.:

ryphimurium, Edition V. Microbial. Sanger, F., Nicklen,

S. and Coulson,

inhibitors.

tools for biological

sequence

Sci. USA 85 (1988) 2444-2448. Linkage

map

of Solmonellu

Rev. 42 (1978) 47 l-511. A.R.: DNA sequencing

Proc. Natl. Acad.

Schendel, F.J., Mueller, E., Stubbe, Formylglycinamide ribonucleotide

E. coli (Schendel et al., 1989). Asterisks denote aa identical in ah three proteins, or end of polypeptide; dashes denote aa shared between the L. casei protein

of the purines,

with chain-

Sci. USA 74 (1977) 5463-

5467.

741 742 (to 1295)

Fig. 3. Comparison

W.R. and Lipman,

terminating

--

J.M.: Biosynthesis

properties of formylglycinamide ribonucleotide from chicken liver. J. Biol. Chem. 243 (1968) 4853-

4862. Pearson,

comparison.

C

.? mHW* R-m

ent organisms.

tt

vm?BaAFm-U

-711 712 978

l

VW7

*

IE Bs EC

IDxQm?...~~Aw __"

K. and Buchanan,

Purification and amido-transferase

that the

Sequences

University

were

of Wiscon-

cloning,

sequencing,

Biochemistry

overproduction,

J., Shiau, synthetase isolation,

A. and Smith, J.M.: from Escherichiu colt and characterization.

28 (1989) 2459-2471.

sequence of the purM gene synthetase of encoding 5’-phosphoribosyl-5-aminoimidazole Escherichia coli K12. J. Biol. Chem. 261 (1986) 10632-10636.

Smith, J.M. and Daum III, H.A.: Nucleotide

Tso, J.Y., Zalkin, H., Van Cleemput, M., Yanofsky, C. and Smith, J.M.: Nucleotide sequence of Escherichiu colipurl; and deduced amino acid sequence

of glutamine

phosphoribosylpyrophosphate

ferase. J. Biol. Chem. 257 (1982) 3525-3531.

amidotrans-