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Isolation, molecular characterization and expression of the ushB gene of Salmonella typhimurium which encodes a membrane‐bound UDP‐sugar hydrolase
Author(s) -
Garrett A. R.,
Johnson L. A.,
Beacham I. R.
Publication year - 1989
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1989.tb01806.x
Subject(s) - periplasmic space , biology , hydrolase , signal peptide , bacterial outer membrane , escherichia coli , salmonella , nucleic acid sequence , gene , biochemistry , homology (biology) , microbiology and biotechnology , peptide sequence , enzyme , genetics , bacteria
Summary The UDP‐sugar hydrolase of Salmonella typhimurium has previously been reported to be located in both the inner and the outer membrane. We have cloned the gene, designated ushB , encoding this enzyme and determined its nucleotide sequence. No significant sequence homology with the periplasmic UDP‐sugar hydrolase of Escherichia coli was found at either the DNA or protein level. However, a sequence is detectable, in the E. coli genome, which weakly hybridizes with a specific ushB probe. Polypeptide analysis has allowed the identification of the Salmonella hydrolase which has an M r of 28349 as compared to an M r of 60767 for the E. coli hydrolase. Most of the protein (∼90%) is located in the inner membrane. Two independent membrane fractionation procedures indicate that the remainder may be associated with the outer membrane. The deduced primary structure indicates the presence of an N ‐terminal signal peptide, although certain features of the region surrounding the putative processing site indicate that processing may be inefficient, or may not occur. Experiments with several inhibitors of signal peptidase function fail to demonstrate the appearance of a precursor form.