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Mol. Biol. Evol. 17(10):14561466. 2000 2000 by the Society for Molecular Biology and Evolution. ISSN: 0737-4038

Summary: 1456
Mol. Biol. Evol. 17(10):1456­1466. 2000
2000 by the Society for Molecular Biology and Evolution. ISSN: 0737-4038
Origin and Evolution of Eukaryotic Chaperonins: Phylogenetic Evidence
for Ancient Duplications in CCT Genes
John M. Archibald, John M. Logsdon Jr.,1 and W. Ford Doolittle
Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada
Chaperonins are oligomeric protein-folding complexes which are divided into two distantly related structural classes.
Group I chaperonins (called GroEL/cpn60/hsp60) are found in bacteria and eukaryotic organelles, while group II
chaperonins are present in archaea and the cytoplasm of eukaryotes (called CCT/TriC). While archaea possess one
to three chaperonin subunit­encoding genes, eight distinct CCT gene families (paralogs) have been characterized
in eukaryotes. We are interested in determining when during eukaryotic evolution the multiple gene duplications
producing the CCT subunits occurred. We describe the sequence and phylogenetic analysis of five CCT genes from
Trichomonas vaginalis and seven from Giardia lamblia, representatives of amitochondriate protist lineages thought
to have diverged early from other eukaryotes. Our data show that the gene duplications producing the eight CCT
paralogs took place prior to the organismal divergence of Trichomonas and Giardia from other eukaryotes. Thus,
these divergent protists likely possess completely hetero-oligomeric CCT complexes like those in yeast and mam-
malian cells. No close phylogenetic relationship between the archaeal chaperonins and specific CCT subunits was
observed, suggesting that none of the CCT gene duplications predate the divergence of archaea and eukaryotes.
The duplications producing the CCT and CCT subunits, as well as CCT , CCT , and CCT , are the most recent


Source: Archibald, John - Department of Biochemistry and Molecular Biology, Dalhousie University
Logsdon Jr., John M., - Department of Biological Sciences, University of Iowa


Collections: Biology and Medicine; Environmental Sciences and Ecology