Molecular evolution of the vesicle coat component βCOP in Toxoplasma gondii

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2007-01
Authors
Smith, Sherri S.
Pfluger, Stacy L.
Hjort, Elizabeth
McArthur, Andrew G.
Hager, Kristin M.
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Coatomer
Beta-COP (β-COP)
Phylogeny
Apicomplexa
Vesicle trafficking
DIVERGE
Functional divergence
Abstract
Coatomer coated (COPI) vesicles play a pivotal role for multiple membrane trafficking steps throughout the eukaryotic cell. Our focus is on βCOP, one of the most well known components of the COPI multi-protein complex. Amino acid differences in βCOP may dictate functional divergence across species during the course of evolution, especially with regards to the evolutionary pressures on obligate intracellular parasites. A bioinformatic analysis of βCOP amino acid sequences was conducted for 49 eukaryotic species. Cloning and sequence analysis of the Toxoplasma gondii βCOP homologue revealed several amino acid insertions unique to T. gondii and one C-terminal insertion that is unique to apicomplexan parasites. These findings led us to investigate the possibility that βCOP experienced functional divergence during the course of its evolution. Bayesian phylogenetic analysis revealed a tree consistent with pan eukaryote distribution and long-branch lengths were observed among the apicomplexans. Further analysis revealed that kinetoplast βCOP underwent the most amount of change, leading to perhaps an overall change of function. In comparison, T. gondii exhibited subtle yet specific amino acid changes. The amino acid substitutions did not occur in the same places as other lineages, suggesting that TgβCOP has a role specific to the apicomplexans. Our work identifies forty-eight residues that are likely to be functionally important when comparing apicomplexan, kinetoplastid, and fungal βCOP.
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Author Posting. © The Author(s), 2007. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Molecular Phylogenetics and Evolution 44 (2007): 1284-1294, doi:10.1016/j.ympev.2007.02.031.
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