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Traditionally, all living organisms have been classified as prokaryotes or eukaryotes. However, the most widely accepted classification now utilizes three major divisions, Archaea (archaebacteria), Bacteria (eubacteria), and Eukarya (eukaryotes).which can then be divided into kingdoms. With either classification system, G. lamblia is clearly a eukaryotic organism and has been considered a member of the protozoa, the more “animal-like” of the unicellular eukaryotes. These protozoan organisms have traditionally been classified by their morphology into flagellates, ciliates, amebae (rhizopods), and sporozoa. Thus, G. lamblia was classified with the flagellated protozoans, including the kinetoplastids (e.g., Leishmania spp. and Trypanosoma spp.), parabasalids (e.g., Trichomonas vaginalis), and Dientamoeba (e.g., Dientamoeba fragilis).Giardia has been placed in the order Diplomonadida (two karyomastigonts, each with four flagella, two nuclei, no mitochondria, and no Golgi complex; cysts are present, and it can be free-living or parasitic)  and the family Hexamitidae (six or eight flagella, two nuclei, bilaterally symmetrical, and sometimes axostyles and median or parabasal bodies), along with the mole parasite Sppironucleus muris.and the free-living organism Hexamita inflata. Some of the higher orders of classification do not appear to be phylogenetically valid, such as the placement of all flagellated protozoans together.On the basis of comparative genomic studies  in yeast, metazoans and higher plants, constituents of the three major coats (COPI, COPII and clathrin), the four SNARE families, GTPase-activating proteins(GAPs), guanine nucleotide exchange factors (GEFs), and NSF ATPases.are demarcated as crucial for conveyance of target molecules and fusion.COPI, COPII, HOPS/CORVET, SEA (Seh1-associated), and clathrin complexes  are significant for the production of transport vesicles and are recruited at the early stages of vesicle formation and fusion .The early secretory pathway in eukaryotes follows a set of sequential and regulated steps within the ER and Golgi apparatus before proteins are directed to the extracellular space or to the cell’s organelles. Structural components of the ER and Golgi apparatus, as well as transportation systems between the two, are present and functional in the P. falciparum parasite.These include budding, transport, docking and fusion machinery of the COPI- and COPII-mediated pathways. COPII coat complex components and TRAPI complex that tethers COPII derived  vesicles to golgi membrane are present in P. falciparum. Though COPI complex components are functional in P. falciparum but DSL1 complex components like DSL1 and Tip20 that tethers COPI vesicles at the ER membrane are not found.    Dsl1 complex is a multi-subunit complex comprises of three subunits, Dsl1, Dsl3/Sec39 and Tip20 and this complex is primarily ER-localized.It contributes as a COPI vesicle-tethering complex in retrograde trafficking from the Golgi apparatus to the endoplasmic reticulum. In G.Intestinalis, DSl1 complex is much simpler consisting of one subunit only .However, blast search using protein coding sequence and specific domain sequence between S.cerevisiae and Giardia lamblia, did not reveal presence of any of the DSl1 subunits in Giardia lamblia.  Dsl1 appears to be missing, but it is typically partially or completely lost inorganisms that lack peroxisomes73. In these cases where very few or no members of a complex could be identified,false negatives due to divergence are much less likely. Entamoeba does not have a ‘stacked’ Golgi body, instead,large Golgi ‘vesicles’ surround the nucleus, as visualized by confocal microscopy of amoebae stained with anti-Arfantibodies74. One may speculate that these potential losses of intra-Golgi and Golgi-ER trafficking machineryare correlated with Entamoeba’s alternative Golgi organelle structure. However, the COPI coat complex, whichalso supports retrograde Golgi-ER trafficking is nearly complete, and almost all subunits have undergone geneduplication events in both Entamoeba species. This suggests that the typical Golgi-to-ER trafficking pathway isfunctional and may even have two functionally distinct COPI coat complexes. Additionally, two paralogues ofthe SM protein that functions in this step are present in both Entamoeba species, lending further support for thistrafficking pathway. These results suggest that Golgi-ER trafficking in Entamoeba differs from what is required inmammalian and yeast cells75,76, in that it is apparently accomplished without the SNAREs and MTCs that tetherincoming vesicles to target membranes in opisthokont system.The Transport protein particle (TRAPPI) complex is a tethering factor for COPII vesicle. TRAPPI is a multisubunit complex that consists of seven subunits (Bet5, Bet3, Trs20, Trs23, Trs31, Trs33, Trs85). The lack of five TRAPPI subunits from Giardia intestinalis may suggest that the TRAPPI complex is nonfunctional in Giardia intestinalis, although interestingly two each of the Bet3 and Bet5 family are present (Koumandou et al., 2007). However, blast search between S.cerevisiae and Giardia lamblia revealed presence of four subunits of TRAPPI like Bet5, Bet3, TRS23, TRS31.Cargo sorting for exit from the ER occurs exclusively at ERES and is mediated by the COPII coat, which binds and concentrates secretory cargoes into vesicles (9, 19, 93, 142, 143, 177,204). COPII recruitment is mediated by the active GTP-bound form of the small GTPase Sar1. Like all GTPases, Sar1 exhibits low intrinsic GDP-to-GTP exchange, and in cells this process is catalyzed by the Sec12 GEF (11, 143, 189). Sec12 is a membrane protein localized to the ER, which restricts Sar1 activation to the ER. Active Sar1 directly binds the Sec23/Sec24 heterodimeric subcomplex of the COPII coat, which in turn recruits the Sec13/Sec31 heterotetrameric subcomplex to the Sec23/Sec24 core Molecular components of COPII includes sar1p, Sec13p, Sec23p1, Sec23p2, Sec23p3,Sec24p, Sec31p, The GGD presents 3 ORFs-GL50803_ 16520, 17065 and 17164- predicted to encode Sec24-related proteins (Marti et al., 2003b). Trypanosomes have orthologues of all the COPII subunits,including two each for Sec23 and Sec24. These subunits form exclusive heterodimers (TbSec23.1/TbSec24.2 and TbSec23.2/TbSec24.1) all colocalizing to one or two ERES per cell . 

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