| Summary: | <p>Abstract</p> <p>Background</p> <p>In <it>Mycoplasma homini</it>s, a facultative human pathogen of the human genital tract, OppA, the substrate-binding domain of the oligopeptide permease, is a multifunctional protein involved in nutrition uptake, cytoadhesion and hydrolysis of extracellular ATP.</p> <p>Results</p> <p>To map the function-related protein regions the ATPase activity and adhesive behavior of OppA mutants were analyzed. Mutations of the Walker BA motifs resulted in an inhibition of up to 8% of the OppA ATPase activity, whereas deletion of the N-terminal CS1 or the CS2 region, structural motifs that are conserved in bacterial OppA proteins, reduced ATPase activity to 60% and deletion of CS3, the third conserved region adjacent to the Walker B motif led to a reduction to 42% ATPase activity.</p> <p>Interestingly, adhesion of the OppA mutants to immobilized HeLa cells demonstrated that two distal regions are mainly involved in adherence of OppA: the CS1 region, deletion of which led to 35% of the cytoadhesion, and the Walker BA with the adjacent upstream region CS3, deletion of which led to 25% of the cytoadhesion. The influence of the ATPase activity on the adherence of <it>M. hominis </it>to HeLa cells was confirmed by the use of ATPase inhibitors which reduced mycoplasmal cytoadhesion to 50%.</p> <p>Conclusions</p> <p>These findings suggest that the OppA-mediated cytoadherence of <it>Mycoplasma homini</it>s depends on both, the topology of the neighbouring CS1 and ATPase domain regions and the functionality of the ecto-ATPase activity in addition.</p>
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