Azotobacter vinelandii gene algJ encodes an outer-membrane protein presumably involved in export of alginate

• Published in: Microbiology (Society for General Microbiology) 1996-04, Vol.142 (4), p.873-880
• Main Author: Rehm, B.H.A
• Format: Article
• Language: English
• Subjects: Alginates - metabolism; Amino Acid Sequence; Azotobacter vinelandii - genetics; Azotobacter vinelandii - metabolism; Bacterial Outer Membrane Proteins - genetics; Bacterial Outer Membrane Proteins - immunology; Bacterial Outer Membrane Proteins - metabolism; Bacterial Proteins - genetics; Bacterial Proteins - immunology; Bacterial Proteins - metabolism; Bacteriology; Base Sequence; Biological and medical sciences; Biological Transport, Active - genetics; Biology of microorganisms of confirmed or potential industrial interest; Biotechnology; Carbohydrate Epimerases - genetics; Cloning, Molecular; Cross Reactions; DNA Primers - genetics; DNA, Bacterial - genetics; Escherichia coli - genetics; Fundamental and applied biological sciences. Psychology; genbank/x86533; Gene Expression; Genes, Bacterial; Genetics; Glucuronic Acid; Hexuronic Acids; Microbiology; Mission oriented research; Molecular Sequence Data; Polymerase Chain Reaction; Protein Structure, Secondary; Sequence Homology, Amino Acid; soil biology; soil science
• ISSN: 1350-0872; 1465-2080
• DOI: 10.1099/00221287-142-4-873

The algJ gene from Azotobacter vinelandii was cloned using a labelled RNA probe representing the coding region of the algE gene from Pseudomonas aeruginosa. DNA sequencing revealed an ORF of 1452 bp encoding a protein of 484 amino acid residues with a calculated molecular mass of 54611 Da. An RNA probe corresponding to algE was also used for Southern hybridization of chromosomal DNA, which showed that algE-related DNA sequences are also present in the alginate-producing phytopathogen species Pseudomonas marginalis and Pseudomonas syringae pv. glycinea. The coding region of algJ was subcloned in the expression vector pT7-7, leading to a corresponding gene product with an apparent molecular mass of 54 kDa which could be identified in the outer membrane (OM) of Escherichia coli BL21(DE3). Additionally, a cross-reacting protein with the same molecular mass was also found in the OM of A. vinelandii using an anti-AlgE antiserum. The derived amino acid sequence of AlgJ shared approximately 52% identity with AlgE from P. aeruginosa. The hydrophilicity profile as well as the amphipathicity of regions in the amino acid sequence of AlgJ showed significant similarities to AlgE. Based on these data, a topological model of AlgJ was created with the aid of known structures of outer-membrane proteins. This model presents AlgJ as a beta-barrel containing 18 beta-strands inserted in the OM.