Affiliation:
1. Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts
Abstract
ABSTRACT
N
-Acetyl-
d
-glucosamine (GlcNAc) is a major component of bacterial cell wall murein and the lipopolysaccharide of the outer membrane. During growth, over 60% of the murein of the side wall is degraded, and the major products, GlcNAc-anhydro-
N
-acetylmuramyl peptides, are efficiently imported into the cytoplasm and cleaved to release GlcNAc, anhydro-
N
-acetylmuramic acid, murein tripeptide (
l
-Ala-
d
-Glu-
meso
-diaminopimelic acid), and
d
-alanine. Like murein tripeptide, GlcNAc is readily recycled, and this process was thought to involve phosphorylation, since GlcNAc-6-phosphate (GlcNAc-6-P) is efficiently used to synthesize murein or lipopolysaccharide or can be metabolized by glycolysis. Since the gene for GlcNAc kinase had not been identified, in this work we purified GlcNAc kinase (NagK) from
Escherichia coli
cell extracts and identified the gene by determining the N-terminal sequence of the purified kinase. A
nagK
deletion mutant lacked phosphorylated GlcNAc in its cytoplasm, and the cell extract of the mutant did not phosphorylate GlcNAc, indicating that NagK is the only GlcNAc kinase expressed in
E. coli
. Unexpectedly, GlcNAc did not accumulate in a
nagK nagEBACD
mutant, though both GlcNAc and GlcNAc-6-P accumulate in the
nagEBACD
mutant, suggesting the existence of an alternative pathway (presumably repressed by GlcNAc-6-P) that reutilizes GlcNAc without the involvement of NagK.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
85 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献