Theoretical studies on peptidoglycans. II. Conformations of the disaccharide-peptide subunit and the three-dimensional structure of peptidoglycan

Abstract

Possible conformations of the disaccharide-peptide subunit of peptidoglycan (of Staphylococcus aureus or Micrococcus luteus) have been studied by an energy-minimization procedure. The favored conformation of the disaccharide N-acetyl-glucosaminyl-β (1-4)-N-acetylmuramic acid (NAG-NAM) is different from that of cellulose or chitin; this disagrees with the assumption of earlier workers. The disaccharide-peptide subunit favors three types of conformations, among which two are compact and the third is extended. All these conformations are stabilized by intramolecular hydrogen bonds. Based on these conformations of the subunit, two different models are proposed for the three-dimensional arrangement of peptidoglycan in the bacterial cell wall.