Molecular evolution of the vesicle coat component βCOP in Toxoplasma gondii
Table 1: Oligonucleotide and gene-specific primers (GSP) used for reverse transcriptase-polymerase chain reaction (RT-PCR), rapid amplification of cDNA ends (RACE), and DNA sequencing (12.83Kb)
Table 2: GenBank accession numbers for βCOP amino acid sequences used to generate multiple sequence alignments and phylogenetic trees, with identity to human βCOP (36.15Kb)
Table 3: Test of the null hypothesis of no change in site-specific evolutionary rates among four clades of βCOP (apicomplexans, kinetoplastids, vertebrates, and fungi), as implemented by the computer program DIVERGE (17.35Kb)
Smith, Sherri S.
Pfluger, Stacy L.
McArthur, Andrew G.
Hager, Kristin M.
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KeywordCoatomer; Beta-COP (β-COP); Phylogeny; Apicomplexa; Vesicle trafficking; DIVERGE; Functional divergence
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.
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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