The bacterial wall peptidogivcao 5a network struc-ture. Clvcart strands of alternate 3,1-4 linked N-ace-tvlglucosamine and N-acetvlmuramic acid pyranoside residues are substituted through the D-lacrvl group of N-acetvlmuramic acid by L-Ala--y-D-Glu-L-Xaa -D-Ala peptideunitswhere L-Xaa3 is most often a diamino acid, occasionally a neutral amino acid. Peptide units substituting adjacent glvcan strands are linked together by means of bridges that involve the carbosyl group of the terminal D-AIa of one peptide and either the w-arnirio group or the diamino acid 1-Xaa3 or the o-carboxyl group of D-Glu of another peptide. De-pending on the composition and location of the bridges, the wall peptidoglycans fall into four main chemotvpes. [The SC/c indicates that this paper has bew~citedin over435 publications.j
March 14, 1989
In the early 1950s, the bacterial cell wall had emerged as a new field
of
research. Milton R.J. Salton had succeeded in isolating the wallsof
several types of bacteria, the first analysesof
which had revealed the occurrence ofcompounds that had never before been encountered in nature. Claes Weibull had ob-served that, upon treatment with lysozyme, resting celIs of Bacillus megaterium were transtormedinto
wall-less, fragile protoplasts, and loshua Lederberg had seen that cellsof
Escherichia coil growing in a hypertonic medium were changed into fragile spher-ical cells when penicillin was added to the culture. Though the underlying mechanisms were different, lysozvme and penicillin brought about a loss of in.tegritv of the wall whose essential function was to keep the bacteria alive under usual environmental conditions.
-I became aware or these studies when, after re-ceiving my PhD in physical chemistry at the Univer-sity of Liege,Icame to Maurice Welsch’s laboratory at the medical school, a place known for its contri-butions to the concept of antibiosis. Welsch had ob-tained from the culture filtrate of Streptomycesaibus
a
crude preparation called actinomycetin, which had bacteriolytic activities. He was convinced that the lytic agent wasof
enzymatic nature, but his at. tempts to isolateithad failed. He probably thought thatImight have better luck.Imet Salton for the first time at the third Interna-tional Congress of Biochemistry in Brussels, in1955,
and the following yearIworked for a few months in his laboratory at the University of Manchester, England. We found that, in marked contrast to lyso-zyme, the wall-degrading activity of two fractions thatIhad laboriously isolated from actinomycetin was attributable to distinct peptidases. The data were illuminating. Possessing the right assortment of hy. drolases should
make
itpossible to establish the structure of the bacterial cell walls by controlled and progressive degradations.Itook about 12 years to carry the project to real achievement. Original hydrolases, each of them hy. drolysing specific linkages, were isolated and used to dismantle, in an ordered manner, the walls
of
various types of bacteria into increasingly smaller fragments. The fragments were isolated, their structure was established, and the “puzzle” wasre-constituted, giving rise to the concept
of
the wall peptidoglycan, a term that, following a roundtable discussion that took place in Detroit, l used for the first time in one of my “biochemistry” papers pub-lished in 1966.Ibelieve that the popularity
of
the article was due to the unified viewitpresented. Despite endless vari-ations in the primary structure, all the bacterial wall peptidoglycans are built on the same general pattern. Simplicity had emerged from a seemingly inextrica-ble complexity.One of the bacteriolytic enzymes described in the article was in fact a OD-carboxypeptidase. This enzyme catalysed an important shift in
my
research and that of my associates as we became interested in a detailed study of this penicillin-resistant metallo (Zn) DO-peptidas&-2 of the serine DD-peptidases, penicillin-binding proteins, and 3.lactamases.MCURRENT CONTENTS®
©1989 by [SI®
cc
,/~
IS,
V. 32, p23, June5, 1989
17_This
Week’s Citation Classic________
Ghuysen J-NI. Use of bacteriolytic enzymes in determination
of wall structure and theirrole in cell metabolism.
Bacteriol. Rev.
32:425-64. [968.[Service de Bacteriologic. Universitd de Liege, Betgtum(
The Rigid Matrix of Bacterial Cell Walls
lean-Marie GhuysenDepartment
of
Microbiology University of Liege8-4000 Liege Belgium
I. Dideberg 0,CharlierP. Dive G. ions B, Frhre i-sI &Ghuyseni-NI. Structure at 2.5 A resolution of a Zn -conraining D-alanvi-O-alanine-cleaving cath5pcptidase. Sort/re 299:469-70. 1982. Cited 30 lImes.) 2. KelI~.1 A. Dideberg 0. Charlier P. Wfrv J P. Libert NI. Nloewn P C. Knox J R, Duet C. Fruipont C, ions B,
Dusart
i,
Frere J-M & Ghuysen i-NI. On the ongin ofbacterial resistanceto penicillin. Comparison of a 3-lactamaseanda penicillin target.Science231: 429-37. 986. iCited 40 times.)3. Duen C, Piron-Fraipont C. ions B. Dusant i. CriSes NI S. Martini i A. Frere .1-NI&Ghuysen I-NI. Primary structure of the Strepromyc-es 561 extraceliular DD-peptidase. I. Cloning into Srrepromvces lii’idans and nacleotide sequence of
he gene. Eur.I. Biochem. 162:509-18. 987.
4. Dideberg 0. Chanlier P. Wery J P. Dehottap P.Dusant
i.
Erpicum 1, Frère i-Nt & Ghuysen i.M, Thecrystal structure of the 5-laccamase of Steepromvcss aibus G at 0.3 ron resolution. Biochemical 3, 245:911-3, 987, 5. ions B. Ghuvseni-Nt. Dive 6. Renard A. Dideberg 0. Charlier P. Frhre i-Nt. KeII~J A, Bovington J C.\Ioews P C & Knox J R, The .,crivc-,ite-ser4i: ~.,,s’~iiin.recoCotzinoenzymes as members of the Streprornrvvs 561 OD-peptidase family. Bioc’hem,c’ai J. 250:313-24. 988.
6. Ghuvsen i-NI. Bacterial active-rite serine penicillin-intrractive proteins and domains: mechanism, structure, and evolution. Re,’ tnt5c. Oh. 0:726-32. 1988.
