Part of respiratory nitrate reductase of Klebsiella aerogenes is intimately associated with the peptidoglycan.
Lysozyme digestion and sonication of sodium dodecyl sulfate (SDS)-purified Klebsiella aerogenes murein sacculi resulted in the quantitative release of both subunits of nitrate reductase, as well as a number of other cytoplasmic membrane polypeptides (5.2%, by weight, of the total membrane proteins). Similar results were obtained after lysozyme digestion of SDS-prepared peptidoglycan fragments, which excluded the phenomenon of simple trapping of the polypeptides by the surrounding peptidoglycan matrix. About 28% of membrane-bound nitrate reductase appears to be tightly associated with the peptidoglycan. Additional evidence for this association was demonstrated by positive immunogold labeling of SDS-murein sacculi and thin sections of plasmolyzed bacteria. Qualitative amino acid analysis of trypsin-treated sacculi, a tryptic product of holo-nitrate reductase, and amino- and carboxypeptidase digests of both nitrate reductase subunits indicated the possible existence of a terminal anchoring peptide containing the following amino acids: (Gly)n, Trp, Ser, Pro, Ile, Leu, Phe, Cys, Tyr, Asp, and Lys.
D000596:Amino Acids / Q000032:analysis; D002462:Cell Membrane / Q000201:enzymology / Q000648:ultrastructure; D007711:Klebsiella pneumoniae / Q000201:enzymology* / Q000648:ultrastructure; D046911:Macromolecular Substances; D009565:Nitrate Reductases / Q000302:isolation & purification*; D010446:Peptide Fragments / Q000032:analysis; D010457:Peptidoglycan / Q000302:isolation & purification*; D014357:Trypsin
D000596:Amino Acids; D046911:Macromolecular Substances; D010446:Peptide Fragments; D010457:Peptidoglycan; D009565:Nitrate Reductases; D014357:Trypsin