title: Biosynthesis of peptidoglycan in Gaffkya homari: processing of nascent glycan by reactivated membranes.
abstract: Membranes from Gaffkya homari reactivated by freezing and thawing were used to study the processing events involved in the assembly of both sodium dodecyl sulfate (SDS)-insoluble peptidoglycan (PG) and SDS-soluble PG. The ability to reactivate membranes for the synthesis of these polymers provided an opportunity to monitor those events that are not influenced by wall-linked PG. In G. homari, processing for the formation of cross-links requires the selective actions of DD-carboxypeptidase, LD-carboxypeptidase, and NE-(DAla)-Lys transpeptidase. Time courses of cross-link formation, as measured by the amounts of amidated bisdisaccharide peptide dimer and nonamidated bisdisaccharide peptide dimer, showed a lack of correlation with those for the synthesis of SDS-insoluble PG. SDS-soluble PG, which is significantly cross-linked when synthesized in the absence of penicillin G, was a precursor of the SDS-insoluble PG. In the presence of penicillin G, un-cross-linked SDS-soluble PG was synthesized. This PG was also utilized and processed for the synthesis of cross-linked SDS-insoluble PG after removal of the beta-lactam. This protocol provided a method for separating stages in the synthesis and elongation of PG from those involved in processing. Cross-linkage in the various PG fractions ranged from 0 to 19% in SDS-soluble PG and from 2 to 24% in SDS-insoluble PG. Thus, the results indicated that there is no direct correlation between SDS insolubility and the degree of cross-linkage. Instead, they suggested that additional features may contribute to the insolubility of PG in SDS.
mesh_terms: D000117:Acetylglucosamine / Q000378:metabolism; D002250:Carbon Radioisotopes; D002462:Cell Membrane / Q000378:metabolism; D007700:Kinetics; D010457:Peptidoglycan / Q000235:genetics*; D011499:Protein Processing, Post-Translational; D013289:Streptococcaceae / Q000378:metabolism*; D014537:Uridine Diphosphate N-Acetylglucosamine / Q000378:metabolism
chemical_list: D002250:Carbon Radioisotopes; D010457:Peptidoglycan; D014537:Uridine Diphosphate N-Acetylglucosamine; D000117:Acetylglucosamine