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Infect Immun. 2008 Nov;76(11):5330-40. doi: 10.1128/IAI.00573-08. Epub 2008 Aug 4.

Modular arrangement of allelic variants explains the divergence in Moraxella catarrhalis UspA protein function.

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1
Department of Molecular Genetics, University of Toronto, Medical Sciences Building, Toronto, Ontario M5S 1A8, Canada.

Abstract

Ubiquitous surface protein A molecules (UspAs) of Moraxella catarrhalis are large, nonfimbrial, autotransporter proteins that can be visualized as a "fuzzy" layer on the bacterial surface by transmission electron microscopy. Previous studies attributed a wide array of functions and binding activities to the closely related UspA1, UspA2, and/or UspA2H protein, yet the molecular and phylogenetic relationships among these activities remain largely unexplored. To address this issue, we determined the nucleotide sequence of the uspA1 genes from a variety of independent M. catarrhalis isolates and compared the deduced amino acid sequences to those of the previously characterized UspA1, UspA2, and UspA2H proteins. Rather than being conserved proteins, we observed a striking divergence of individual UspA1, UspA2, and UspA2H proteins resulting from the modular assortment of unrelated "cassettes" of peptide sequence. The exchange of certain variant cassettes correlates with strain-specific differences in UspA protein function and confers differing phenotypes upon these mucosal surface pathogens.

PMID:
18678659
PMCID:
PMC2573364
DOI:
10.1128/IAI.00573-08
[Indexed for MEDLINE]
Free PMC Article
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