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The role of the intracellular inhibitor of periplasmic UDP‐sugar hydrolase (5′‐nucleotidase) in Escherichia coli : cytoplasmic localisation of 5′‐nucleotidase is conditionally lethal
Author(s) -
Innes David,
Beacham Ifor R.,
Burns Dennis M.
Publication year - 2001
Publication title -
journal of basic microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.58
H-Index - 54
eISSN - 1521-4028
pISSN - 0233-111X
DOI - 10.1002/1521-4028(200112)41:6<329::aid-jobm329>3.0.co;2-4
Subject(s) - 5' nucleotidase , cytoplasm , hydrolase , intracellular , periplasmic space , nucleotidase , biochemistry , biology , ribonuclease , enzyme , microbiology and biotechnology , chemistry , escherichia coli , rna , gene
E. coli UshA, a bifunctional enzyme with UDP‐sugar hydrolase and 5′‐nucleotidase activities, is secreted to the periplasm but has a specific protein inhibitor located in the cytoplasm. It has been previously suggested that some 5′‐nucleotidase, or a folded domain of this enzyme, may be active in the cytoplasm prior to export. If true, the intracellular inhibitor may have a role in protecting the cell from the likely deleterious effects of any intracellular UshA activity. Using deletion mutagenesis to remove the UshA signal peptide, we have shown that the resulting UshA derivative is an active cytoplasmic 5′‐nucleotidase, and causes conditional lethality. Our results support the hypothesis that the physiological role of the UshA inhibitor is to protect the intracellular nucleotide pool from any cytoplasmic 5′‐nucleotidase activity.