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Journal of Bacteriology, January 2007, p. 76-82, Vol. 189, No. 1
0021-9193/07/$08.00+0 doi:10.1128/JB.00788-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Department of Medical Genetics and Microbiology, University of Toronto, Toronto, Canada M5S 1A8,1 Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas 753902
Received 1 June 2006/ Accepted 5 October 2006
Moraxella catarrhalis is a human-restricted pathogen that can cause respiratory tract infections. In this study, we identified a previously uncharacterized 24-kDa outer membrane protein with a high degree of similarity to Neisseria Opa protein adhesins, with a predicted ß-barrel structure consisting of eight antiparallel ß-sheets with four surface-exposed loops. In striking contrast to the antigenically variable Opa proteins, the M. catarrhalis Opa-like protein (OlpA) is highly conserved and constitutively expressed, with 25 of 27 strains corresponding to a single variant. Protease treatment of intact bacteria and isolation of outer membrane vesicles confirm that the protein is surface exposed yet does not bind host cellular receptors recognized by neisserial Opa proteins. Genome-based analyses indicate that OlpA and Opa derive from a conserved family of proteins shared by a broad array of gram-negative bacteria.
Published ahead of print on 13 October 2006.
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