F
IPR008088

Alpha giardin

InterPro entry
Short nameAlpha_giardin
Overlapping
homologous
superfamilies
 

Description

Giardia lamblia (Giardia intestinalis) is a protozoan parasite of numerous mammals, including Homo sapiens
[3]
. It belongs to the phylum Sarcomastigophora, and is amongst the most primitive eukaryotes identified to date. It is the main causative agent of global protozoan diarrhoea, and severe infection can cause giardiasis. G. lamblia exists as either trophozoites that live in the small intestine of the host and cause the disease symptoms, or cysts that are passed in the faeces of the host and infect the next host through contaminated water or food
[3]
.

Trophozoites exhibit antigenic variation to evade the host immune system, expressing a number of virulence factors to aid adherence and invasion of the small intestine endothelium
[1]
. The molecular basis for its antigenic variation has been well characterised, and it is believed that its phenotypic heretogeneity arises from sexual reproduction
[1]
. One of the major virulence factors of G. lamblia is giardin, an antigen expressed as several variants on the trophozoite surface
[4]
. Alpha giardin is the predominant immunotypic giardin present, although beta and gamma giardin have also been identified
[4]
.

This entry represents a family of alpha giardin proteins specific to Giardia. The biochemical properties of the subunit identify the protein as an annexin, a eukaryotic protein widely conserved amongst plants and animals. This protein associates with phosphatidyl serine-containing vesicles in a Ca2+-dependent manner, and has very low sequence similarity with human annexin XIX
[2]
. This protein shows a fourfold cyclic configuration of five-helix bundles with repeats I/IV, and II/III each forming a module. The canonical membrane binding site of the annexins is located on the convex side of the molecule
[5]
.

References

1.Giardiasis. Taming this pervasive parasitic infection. Babb RR. 98, 155-8, (1995). PMID: 7630843

2.Functional identification of alpha 1-giardin as an annexin of Giardia lamblia. Bauer B, Engelbrecht S, Bakker-Grunwald T, Scholze H. FEMS Microbiol. Lett. 173, 147-53, (1999). PMID: 10220891

3.Biology of Giardia lamblia. Adam RD. Clin. Microbiol. Rev. 14, 447-75, (2001). View articlePMID: 11432808

4.Characterization of an immunodominant Giardia lamblia protein antigen related to alpha giardin. Wenman WM, Meuser RU, Nyugen Q, Kilani RT, el-Shewy K, Sherburne R. Parasitol. Res. 79, 587-92, (1993). View articlePMID: 8278341

5.Alpha-1 giardin is an annexin with highly unusual calcium-regulated mechanisms. Weeratunga SK, Osman A, Hu NJ, Wang CK, Mason L, Svard S, Hope G, Jones MK, Hofmann A. J. Mol. Biol. 423, 169-81, (2012). PMID: 22796298

Further reading

6. Amino acid sequence analysis of the annexin super-gene family of proteins. Barton GJ, Newman RH, Freemont PS, Crumpton MJ. Eur. J. Biochem. 198, 749-60, (1991). View articlePMID: 1646719

7. The annexins. Moss SE, Morgan RO. Genome Biol. 5, 219, (2004). View articlePMID: 15059252

GO terms

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