| Abstract: | The function of UreC, the product of a 1,335-bp-long open reading frame upstream from the urease structural genes (ureAB) of Helicobacter pylori, was investigated. We present data showing that the ureC gene product is a phosphoglucosamine mutase. D. Mengin-Lecreulx and J. van Heijenoort (J. Biol. Chem. 271:32-39, 1996) observed that UreC is similar (43% identity) to the GlmM protein of Escherichia coli. Those authors showed that GlmM is a phosphoglucosamine mutase catalyzing interconversion of glucosamine-6-phosphate into glucosamine-1-phosphate, which is subsequently transformed into UDP-N-acetylglucosamine. The latter product is one of the main cytoplasmic precursors of cell wall peptidoglycan and outer membrane lipopolysaccharides. The present paper reports that, like its E. coli homolog glmM, the H. pylori ureC gene is essential for cell growth. It was known that growth of a lethal conditional glmM mutant of E. coli at a nonpermissive temperature can be restored in the presence of the ureC gene. We showed that complete complementation of the glmM mutant can be obtained with a plasmid overproducing UreC. The peptidoglycan content and the specific phosphoglucosamine mutase activity of such a complemented strain were measured; these results demonstrated that the ureC gene product functions as a phosphoglucosamine mutase. Homologs of the UreC and GlmM proteins were identified in Haemophilus influenzae, Mycobacterium leprae, Clostridium perfringens, Synechocystis sp. strain PCC6803, and Methanococcus jannaschii. Significant conservation of the amino acid sequence of these proteins in such diverse organisms suggests a very ancient common ancestor for the genes and defines a consensus motif for the phosphoglucosamine mutase active site. We propose renaming the H. pylori ureC gene the glmM gene. |
