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Cloning and sequencing of Escherichia coli ubiC and purification of chorismate lyase.

ABSTRACT: In Escherichia coli, chorismate lyase catalyzes the first step in ubiquinone biosynthesis, the conversion of chorismate to 4-hydroxybenzoate. 4-Hydroxybenzoate is converted to 3-octaprenyl-4-hydroxybenzoate by 4-hydroxybenzoate octaprenyltransferase. These two enzymes are encoded by ubiC and ubiA, respectively, and have been reported to map near one another at 92 min on the E. coli chromosome. We have cloned the ubiCA gene cluster and determined the nucleotide sequence of ubiC and a portion of ubiA. The nucleotide sequence abuts with a previously determined sequence that encodes a large portion of ubiA. ubiC was localized by subcloning, and overproducing plasmids were constructed. Overexpression of ubiC allowed the purification of chorismate lyase to homogeneity, and N-terminal sequence analysis of chorismate lyase unambiguously defined the beginning of the ubiC coding region. Although chorismate lyase showed no significant amino acid sequence similarity to 4-amino-4-deoxychorismate lyase (4-amino-4-deoxychroismate----4-aminobenzoate), the product of E. coli pabC, chorismate lyase overproduction could complement the growth requirement for 4-aminobenzoate of a pabC mutant strain. Of the several enzymes that convert chorismate to intermediates of E. coli biosynthetic pathways, chorismate lyase is the last to be isolated and characterized.

SUBMITTER: Nichols BP

PROVIDER: S-EPMC206367 | biostudies-other | 1992 Aug

REPOSITORIES: biostudies-other

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Cloning and sequencing of Escherichia coli ubiC and purification of chorismate lyase.

Nichols B P BP Green J M JM

Journal of bacteriology 19920801 16

In Escherichia coli, chorismate lyase catalyzes the first step in ubiquinone biosynthesis, the conversion of chorismate to 4-hydroxybenzoate. 4-Hydroxybenzoate is converted to 3-octaprenyl-4-hydroxybenzoate by 4-hydroxybenzoate octaprenyltransferase. These two enzymes are encoded by ubiC and ubiA, respectively, and have been reported to map near one another at 92 min on the E. coli chromosome. We have cloned the ubiCA gene cluster and determined the nucleotide sequence of ubiC and a portion of u ...[more]

PMID: 1644758

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Project description:The Escherichia coli K5 capsular polysaccharide [-4)-betaGlcA-(1, 4)-alphaGlcNAc-(1-] is a receptor for the capsule-specific bacteriophage K5A. Associated with the structure of bacteriophage K5A is a polysaccharide lyase which degrades the K5 capsule to expose the underlying bacterial cell surface. The bacteriophage K5A lyase gene (kflA) was cloned and sequenced. The kflA gene encodes a polypeptide with a predicted molecular mass of 66.9 kDa and which exhibits amino acid homology with ElmA, a K5 polysaccharide lyase encoded on the chromosome of E. coli SEBR 3282. There was only limited nucleotide homology between the kflA and elmA genes, suggesting that these two genes are distinct and either have been derived from separate progenitors or have diverged from a common progenitor for a considerable length of time. Southern blot analysis revealed that kflA was not present on the chromosome of the E. coli strains examined. In contrast, elmA was present in a subset of E. coli strains. Homology was observed between DNA flanking the kflA gene of bacteriophage K5A and DNA flanking a small open reading frame (ORF(L)) located 5' of the endosialidase gene of the E. coli K1 capsule-specific bacteriophage K1E. The DNA homology between these noncoding sequences indicated that bacteriophages K5A and K1E were related. The deduced polypeptide sequence of ORF(L) in bacteriophage K1E exhibited homology to the N terminus of KflA from bacteriophage K5A, suggesting that ORF(L) is a truncated remnant of KflA. The presence of this truncated kflA gene implies that bacteriophage K1E has evolved from bacteriophage K5A by acquisition of the endosialidase gene and subsequent loss of functional kflA. A (His)(6)-KflA fusion protein was overexpressed in E. coli and purified to homogeneity with a yield of 4.8 mg per liter of bacterial culture. The recombinant enzyme was active over a broad pH range and NaCl concentration and was capable of degrading K5 polysaccharide into a low-molecular-weight product.

Dataset Information

Cloning and sequencing of Escherichia coli ubiC and purification of chorismate lyase.

Publications

Cloning and sequencing of Escherichia coli ubiC and purification of chorismate lyase.

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