| Summary: | <p>Abstract</p> <p>Background</p> <p>Hsp-90 from the free-living nematode <it>Caenorhabditis elegans </it>is unique in that it fails to bind to the specific Hsp-90 inhibitor, geldanamycin (GA). Here we surveyed 24 different free-living or parasitic nematodes with the aim of determining whether <it>C. elegans </it>Hsp-90 was the exception or the norm amongst the nematodes. We combined these data with codon evolution models in an attempt to identify whether <it>hsp-90 </it>from GA-binding and non-binding species has evolved under different evolutionary constraints.</p> <p>Results</p> <p>We show that GA-binding is associated with life history: free-living nematodes and those parasitic species with free-living larval stages failed to bind GA. In contrast, obligate parasites and those worms in which the free-living stage in the environment is enclosed within a resistant egg, possess a GA-binding Hsp-90. We analysed Hsp-90 sequences from fifteen nematode species to determine whether nematode <it>hsp-90</it>s have undergone adaptive evolution that influences GA-binding. Our data provide evidence of rapid diversifying selection in the evolution of the <it>hsp-90 </it>gene along three separate lineages, and identified a number of residues showing significant evidence of adaptive evolution. However, we were unable to prove that the selection observed is correlated with the ability to bind geldanamycin or not.</p> <p>Conclusion</p> <p>Hsp-90 is a multi-functional protein and the rapid evolution of the <it>hsp-90 </it>gene presumably correlates with other key cellular functions. Factors other than primary amino acid sequence may influence the ability of Hsp-90 to bind to geldanamycin.</p>
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