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Molecular analysis of an outer membrane protein, MopB, of Methylococcus capsulatus (Bath) and structural comparisons with proteins of the OmpA family
- Fjellbirkeland, Anne, Bemanian, Vahid, McDonald, Ian R., Murrell, J. Colin, Jensen, Harald B.
- Archives of microbiology 2000 v.173 no.5-6 pp. 346-351
- DNA, Methylococcus capsulatus, Methylomonas methanica, Pseudomonas aeruginosa, databases, fluorescent labeling, genes, open reading frames, outer membrane proteins, polypeptides, sequence homology, signal peptide
- The gene encoding a major outer membrane protein (MopB) of the methanotroph Methylococcus capsulatus (Bath) was cloned and sequenced. The cloned DNA contained an open reading frame of 1044 bp coding for a 348-amino-acid polypeptide with a 21-amino-acid leader peptide. Comparative sequence analysis of the predicted amino acid sequence revealed that the C-terminal part of MopB possessed sequences that are conserved in the OmpA family of proteins. The N-terminal half of the protein had no significant sequence similarity to other proteins in the databases, but the predicted secondary structure showed stretches of amphipathic β-strands typical of transmembrane segments of outer membrane proteins. A region with four cysteines similar to the cysteine-encompassing region of the OprF of Pseudomonas aeruginosa was found toward the C-terminal part of MopB. Results from whole-cell labeling with the fluorescent thiol-reacting reagent 5-iodoacetamidofluorescein indicated a surface-exposed location for these cysteines. A probe consisting of the 3′-end of the mopB gene hybridized to the type I methanotroph Methylomonas methanica S1 in Southern blots containing DNA from nine methanotrophic strains representing six different genera.