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J. Bacteriol., Nov 1996, 6451-6458, Vol 178, No. 22
DL Popham, J Helin, CE Costello and P Setlow
Peptidoglycan was prepared from purified Bacillus subtilis spores of
wild-type and several mutant strains. Digestion with muramidase resulted in
cleavage of the glycosidic bonds adjacent to muramic acid replaced by
peptide or alanine side chains but not the bonds adjacent to muramic
lactam. Reduction of the resulting muropeptides allowed their separation by
reversed-phase high-pressure liquid chromatography. The structures of 20
muropeptides were determined by amino acid and amino sugar analysis and
matrix-assisted laser desorption/ionization time-of-flight mass
spectrometry. In wild-type spores, 50% of the muramic acid had been
converted to the lactam and 75% of these lactam residues were spaced
regularly at every second muramic acid position in the glycan chains.
Single L-alanine side chains were found on 25% of the muramic acid
residues. The remaining 25% of the muramic acid had tetrapeptide or
tripeptide side chains, and 11% of the diaminopimelic acid in these side
chains was involved in peptide cross-links. Analysis of spore peptidoglycan
produced by a number of mutants lacking proteins involved in cell wall
metabolism revealed structural changes. The most significant changes were
in the spores of a dacB mutant which lacks the sporulation-specific
penicillin-binding protein 5*. In these spores, only 46% of the muramic
acid was in the lactam form, 12% had L-alanine side chains, and 42% had
peptide side chains containing diaminopimelic acid, 29% of which was
involved in cross-links.
Copyright © 1996, American Society for Microbiology
Analysis of the peptidoglycan structure of Bacillus subtilis endospores
Department of Biochemistry, University of Connecticut Health Center, Farmington 06030-3305, USA.
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