Abstract
BackgroundProtein secretion is an essential process in all eukaryotes including organisms belonging to the phylum Apicomplexa, which includes many intracellular parasites. The apicomplexan parasites possess a specialized collection of secretory organelles that release a number of proteins to facilitate the invasion of host cells and some of these proteins also participate in immune evasion. Like in other eukaryotes, these parasites possess a series of membrane-bound compartments, namely the endoplasmic reticulum (ER), the intermediate compartments (IC) or vesicular tubular clusters (VTS) and Golgi complex through which proteins pass in a sequential and vectorial fashion. Two sets of proteins; COPI and COPII are important for directing the sequential transfer of material between the ER and Golgi complex.ResultsHere, using in silico approaches, we identify the components of COPI and COPII complexes in the genome of apicomplexan organisms. The results showed that the COPI and COPII protein complexes are conserved in most apicomplexan genomes with few exceptions. Diversity among the components of COPI and COPII complexes in apicomplexan is either due to the absence of a subunit or due to the difference in the number of protein domains. For example, the COPI epsilon subunit and COPII sec13 subunit is absent in Babesia bovis, Theileria parva, and Theileria annulata genomes. Phylogenetic and domain analyses for all the proteins of COPI and COPII complexes was performed to predict their evolutionary relationship and functional significance.ConclusionsThe study thus provides insights into the apicomplexan COPI and COPII coating machinery, which is crucial for parasites secretory network needed for the invasion of host cells.
Highlights
Protein secretion is an essential process in all eukaryotes including organisms belonging to the phylum Apicomplexa, which includes many intracellular parasites
There were 11 different Pfam domains traced to be distributed in COPI and COPII proteins (Table 1 and Table 2) of various model organisms that were used as query Pfam profiles
We screened the proteomes of apicomplexan parasites using in silico computational approaches and identified all the subunits of COPI and COPII complexes
Summary
Protein secretion is an essential process in all eukaryotes including organisms belonging to the phylum Apicomplexa, which includes many intracellular parasites. Two sets of proteins; COPI and COPII are important for directing the sequential transfer of material between the ER and Golgi complex. The Apicomplexa includes a number of obligate intracellular parasites such as Plasmodium, Cryptosporidium, Theileria, Eimeria and Neospora that are of medical and agricultural significance [1]. This phylum is divided into five principal groups: Haemosporidia, Piroplasmorida, Coccidia, Gregarinasina, and Cryptosporidium [2]. Membrane binding of Sar1p-GTP recruits Sec23/24p heterodimer sub-complex that in turn recruits Sce13/31 heterodimer subcomplex of COPII results the deformation into buds and to vesicles [7]. The arrangements of the subunits of COPI and COPII are depicted in a schematic diagram (Fig. 1)
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