Molecular characterization of the ATPase component of a putative ABC type transporter in moraxella catarrhalis

Abstract

Moraxella catarrhalis is one of the major causes of respiratory tract and middle ear infections. Little is known about the pathogenesis of M. catarrhalis infection. A pathogenic bacterium requires adherence, invasion, establishment and dissemination with the host for a successful infection. The interaction between the host and the pathogen also includes uptake and secretion of substances that are facilitated by a family of proteins termed transporters. ATP-binding cassette (ABC) transporter is one of the active transport system common in prokaryotic and eukaryotic cells. In this study, we identified a gene encoding ATPase component of the ABC type transporter in M. catarrhalis and performed a nucleotide and deduced amino acid sequence analysis of this gene. We used Genomic Survey Sequence approach (GSS) to identify the gene from M. catarrhalis genomic library. The insert size of the positive clone is 934 bp and was sequenced by DNA walking. The ATPase domain of an ABC type transporter has conserved motifs: Walker A, Q loop, C loop (signature sequence), Walker B, D loop and Switch II. The ATPase domain is considered as the most conserved domain of the ABC type transporter due to presence of these motifs. Based on the homology and motif search, and amino acid sequence alignment, performed by using BLAST programs available on the internet, it was found that the deduced amino acid sequence encoded by this gene exhibited 50-80% identity with the sequences of the ATPase component of the ABC transporters of several pathogens.