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Infect. Immun. doi:10.1128/IAI.00396-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Identification of a novel two-partner secretion locus in Moraxella catarrhalis

Department of Microbiology and Immunology and Department of Medicine, Division of Infectious Disease, Witebsky Center for Microbial Pathogenesis and Immunology, University at Buffalo, State University of New York, NYS Center of Excellence in Bioinformatics and Life Sciences, Buffalo, New York

^* To whom correspondence should be addressed. Email: AAC{at}acsu.buffalo.edu.

	Abstract

Although Moraxella catarrhalis continues to be a significant cause of disease in both children and adults, the steps involved in pathogenesis remain poorly understood. We have identified three open reading frames (ORFs) in the M. catarrhalis genome that encode for homologues of the two-partner secretion system (TPS). The sequenced M. catarrhalis hemagglutinin-like (MCH) locus of strain 7169 has a unique gene organization composed in the order of mchA1, mchB, and mchA2, where mchA1 is divergent. MchA1 and MchA2 are 74% identical at the amino acid level and diverge only in the C-terminal regions. The TPS motif identified in the common N-terminal region of MchA1 and MchA2 was found to be homologous to the filamentous hemagglutinin of Bordetella pertussis, MchB has homology to other TpsB transporters. The presence of MchA1 and MchA2 in outer membrane protein preparation and concentrated culture supernatant (CCS) of strain 7169 was confirmed by immunoblot using specific antisera. NanoLC-MS/MS peptide sequencing was performed on the antibody reactive band in the CCS demonstrating that 13 different peptides mapped to identical regions of MchA1 and MchA2. Quantitative adherence assays demonstrated a decrease of binding to primary normal human bronchial epithelial cells by the mch mutants 7169mchB and 7169mchA1A2B as compared to the wild type strain. These studies demonstrate that MchA1, MchA2 and MchB are components of a novel TPS system identified in M. catarrhalis and suggest that these proteins may be involved in colonization.

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