<p>This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.</p> <p>The peptidyl-prolyl <italic>cis/trans</italic> isomerase (PPIase) class of proteins comprises three
member families that are found throughout nature and are present in all the major
compartments of the cell. Their numbers appear to be linked to the number of genes in
their respective genomes, although we have found the human repertoire to be smaller
than expected due to a reduced cyclophilin repertoire. We show here that whilst the
members of the cyclophilin family (which are predominantly found in the nucleus
and cytoplasm) and the parvulin family (which are predominantly nuclear) are
largely conserved between different repertoires, the FKBPs (which are predominantly
found in the cytoplasm and endoplasmic reticulum) are not. It therefore appears
that the cyclophilins and parvulins have evolved to perform conserved functions,
while the FKBPs have evolved to fill ever-changing niches within the constantly
evolving organisms. Many orthologous subgroups within the different PPIase families
appear to have evolved from a distinct common ancestor, whereas others, such as the
mitochondrial cyclophilins, appear to have evolved independently of one another. We
have also identified a novel parvulin within <italic>Drosophila melanogaster</italic> that is unique to
the fruit fly, indicating a recent evolutionary emergence. Interestingly, the fission yeast
repertoire, which contains no unique cyclophilins and parvulins, shares no PPIases
solely with the budding yeast but it does share a majority with the higher eukaryotes
in this study, unlike the budding yeast. It therefore appears that, in comparison with
<italic>Schizosaccharomyces pombe, Saccharomyces cerevisiae</italic> is a poor representation of the
higher eukaryotes for the study of PPIases.</p>
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Comp Funct Genomics. 2005 Jul-Aug; 6(5-6):277-300