The elucidation of the structure of Thermotoga maritima peptidoglycan reveals two novel types of cross-link.
Thermotoga maritima is a Gram-negative, hyperthermophilic bacterium whose peptidoglycan contains comparable amounts of L- and D-lysine. We have determined the fine structure of this cell-wall polymer. The muropeptides resulting from the digestion of peptidoglycan by mutanolysin were separated by high-performance liquid chromatography and identified by amino acid analysis after acid hydrolysis, dinitrophenylation, enzymatic determination of the configuration of the chiral amino acids, and mass spectrometry. The high-performance liquid chromatography profile contained four main peaks, two monomers, and two dimers, plus a few minor peaks corresponding to anhydro forms. The first monomer was the d-lysine-containing disaccharide-tripeptide in which the D-Glu-D-Lys bond had the unusual gamma-->epsilon arrangement (GlcNAc-MurNAc-L-Ala-gamma-D-Glu-epsilon-D-Lys). The second monomer was the conventional disaccharide-tetrapeptide (GlcNAc-MurNAc-L-Ala-gamma-D-Glu-L-Lys-D-Ala). The first dimer contained a disaccharide-L-Ala as the acyl donor cross-linked to the alpha-amine of D-Lys in a tripeptide acceptor stem with the sequence of the first monomer. In the second dimer, donor and acceptor stems with the sequences of the second and first monomers, respectively, were connected by a D-Ala4-alpha-D-Lys3 cross-link. The cross-linking index was 10 with an average chain length of 30 disaccharide units. The structure of the peptidoglycan of T. maritima revealed for the first time the key role of D-Lys in peptidoglycan synthesis, both as a surrogate of L-Lys or meso-diaminopimelic acid at the third position of peptide stems and in the formation of novel cross-links of the L-Ala1(alpha-->alpha)D-Lys3 and D-Ala4(alpha-->alpha)D-Lys3 types.
Boniface
Audrey
A
Laboratoire des Enveloppes Bactériennes et Antibiotiques, Institut de Biochimie et Biophysique Moléculaire et Cellulaire, Université Paris-Sud, 91405 Orsay; CNRS, UMR 8619, 91405 Orsay.
Parquet
Claudine
C
Laboratoire des Enveloppes Bactériennes et Antibiotiques, Institut de Biochimie et Biophysique Moléculaire et Cellulaire, Université Paris-Sud, 91405 Orsay; CNRS, UMR 8619, 91405 Orsay.
Arthur
Michel
M
Centre de Recherche des Cordeliers, Laboratoire de Recherche Moléculaire sur les Antibiotiques, Université Pierre et Marie Curie, UMR S 872, 75006 Paris; Université Paris-Descartes, UMR S 872, 75006 Paris; INSERM, U872, 75006 Paris, France.
Mengin-Lecreulx
Dominique
D
Laboratoire des Enveloppes Bactériennes et Antibiotiques, Institut de Biochimie et Biophysique Moléculaire et Cellulaire, Université Paris-Sud, 91405 Orsay; CNRS, UMR 8619, 91405 Orsay.
Blanot
Didier
D
Laboratoire des Enveloppes Bactériennes et Antibiotiques, Institut de Biochimie et Biophysique Moléculaire et Cellulaire, Université Paris-Sud, 91405 Orsay; CNRS, UMR 8619, 91405 Orsay.
D000409:Alanine / Q000737:chemistry; D002473:Cell Wall / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003432:Cross-Linking Reagents / Q000494:pharmacology*; D004187:Disaccharides / Q000737:chemistry; D010450:Endopeptidases / Q000737:chemistry; D008239:Lysine / Q000737:chemistry; D013058:Mass Spectrometry / Q000379:methods; D008956:Models, Chemical; D010455:Peptides / Q000737:chemistry; D010457:Peptidoglycan / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D011134:Polysaccharides / Q000737:chemistry; D020124:Thermotoga maritima / Q000378:metabolism*; D013997:Time Factors
D003432:Cross-Linking Reagents; D004187:Disaccharides; D010455:Peptides; D010457:Peptidoglycan; D011108:Polymers; D011134:Polysaccharides; D010450:Endopeptidases; C021816:mutanolysin; D008239:Lysine; D000409:Alanine