This entry includes flavin carrier proteins Flc1-3 from budding yeasts and Pkd2 from fission yeasts. They are transient receptor potential channel-like proteins. Flc1 may be responsible for the transport of FAD into the endoplasmatic reticulum lumen, where it is required for oxidative protein folding []. Pkd2 acts as a key signaling component in the regulation of cell shape and cell wall synthesis through interaction with GTPase Rho1 [].
This entry represents the polycystin domain from group II of Transient receptor potential (TRP) channels (TRPP) including PKD1, PKD2 and PKD2L. The polycystin domain displays a sandwich-like shape with five β-sheets in the tilted middle layer, three α-helices on one side, and a large loop with two short antiparallel β-sheets on the other [].
This domain is distantly similar to MD-2-related lipid-recognition domain () and conserves its pattern of conserved cysteines. This suggests that this domain may be involved in lipid binding. Proteins containing this domain include flavin carrier protein 1/2 from budding yeasts []and TRP-like ion channel pkd2 from fission yeasts [].
Polycystic kidney diseases (PKD) are disorders characterised by large numbers of cysts distributed throughout grossly-enlarged kidneys. Cystdevelopment is associated with impairment of kidney function, and ultimately kidney failure and death [, ]. Most cases of autosomal dominant PKD result from mutations in the PKD1 gene that cause premature protein termination. A second gene for autosomal dominant polycystic kidney disease has been identified by positional cloning []. The predicted 968-amino acid sequence of the PKD2 gene product (polycystin-2) contains 6 transmembrane domains, with intracellular N- and C-termini. Polycystin-2 shares some similarity with the family of voltage-activated calcium (and sodium) channels, and contains a potential calcium-binding domain [].Polycystin-2 is strongly expressed in ovary, foetal and adult kidney, testis, and small intestine. Polycystin-1 requires the presence of this protein for stable expression and is believed to interact with it via its C terminus. All mutations between exons 1 and 11 result in a truncated polycystin-2 that lacks a calcium-binding EF-hand domain and the cytoplasmic domains required for the interaction of polycystin-2 with polycystin-1 []. PKD2, although clinically milder than PKD1, has a deleterious impact on life expectancy.This entry contains proteins belonging to the polycystin family including Mucolipin and Polycystin-1 and -2 (PKD1 and PKD2). The domain contains the cation channel region of PKD1 and PKD2 proteins. PKD1 and PKD2 may function through a common signalling pathway that is necessary for normal tubulogenesis. The PKD2 gene product has six transmembrane spans with intracellular amino- and carboxyl-termini [].Mucolipin is a cationic channel which probably plays a role in the endocytic pathway and in the control of membrane trafficking of proteins and lipids. It could play a major role in the calcium ion transport regulating lysosomal exocytosis [, , ].
Polycystic kidney diseases (PKD) are disorders characterised by large numbers of cysts distributed throughout grossly-enlarged kidneys. Cystdevelopment is associated with impairment of kidney function, and ultimately kidney failure and death [, ]. Most cases of autosomal dominant PKD result from mutations in the PKD1 gene that cause premature protein termination. A second gene for autosomal dominant polycystic kidney disease has been identified by positional cloning []. The predicted 968-amino acid sequence of the PKD2 gene product (polycystin-2) contains 6 transmembrane domains, with intracellular N- and C-termini. Polycystin-2 shares some similarity with the family of voltage-activated calcium (and sodium) channels, and contains a potential calcium-binding domain [].Polycystin-2 is strongly expressed in ovary, foetal and adult kidney, testis, and small intestine. Polycystin-1 requires the presence of this protein for stable expression and is believed to interact with it via its C terminus. All mutations between exons 1 and 11 result in a truncated polycystin-2 that lacks a calcium-binding EF-hand domain and the cytoplasmic domains required for the interaction of polycystin-2 with polycystin-1 []. PKD2, although clinically milder than PKD1, has a deleterious impact on life expectancy.
