Cloning and Expression of Three New Azotobacter vinelandii Genes Closely Related to a Previously Described Gene Family Encoding Mannuronan C-5-Epimerases

AUTOR(ES)

Svanem, Britt Iren Glærum

FONTE

American Society for Microbiology

RESUMO

The cloning and expression of a family of five modular-type mannuronan C-5-epimerase genes from Azotobacter vinelandii (algE1 to -5) has previously been reported. The corresponding proteins catalyze the Ca2+-dependent polymer-level epimerization of β-d-mannuronic acid to α-l-guluronic acid (G) in the commercially important polysaccharide alginate. Here we report the identification of three additional structurally similar genes, designated algE6, algE7, and algY. All three genes were sequenced and expressed in Escherichia coli. AlgE6 introduced contiguous stretches of G residues into its substrate (G blocks), while AlgE7 acted as both an epimerase and a lyase. The epimerase activity of AlgE7 leads to formation of alginates with both single G residues and G blocks. AlgY did not display epimerase activity, but a hybrid gene in which the 5′-terminal part was exchanged with the corresponding region in algE4 expressed an active epimerase. Southern blot analysis of genomic A. vinelandii DNA, using the 5′ part of algE2 as a probe, indicated that all hybridization signals originated from algE1 to -5 or the three new genes reported here.

Documentos Relacionados

• Cloning and expression of an Azotobacter vinelandii mannuronan C-5-epimerase gene.
• A new Azotobacter vinelandii mannuronan C-5-epimerase gene (algG) is part of an alg gene cluster physically organized in a manner similar to that in Pseudomonas aeruginosa.
• Temperature-Dependent Regulation by Molybdenum and Vanadium of Expression of the Structural Genes Encoding Three Nitrogenases in Azotobacter vinelandii
• Cloning, characterization, and expression in Escherichia coli of the genes encoding the cytochrome d oxidase complex from Azotobacter vinelandii.
• The A Modules of the Azotobacter vinelandii Mannuronan-C-5-Epimerase AlgE1 Are Sufficient for both Epimerization and Binding of Ca2+