Inorganic phosphate transporter family
The inorganic phosphate transporter (PiT) family is a group of carrier proteins derived from Gram-negative and Gram-positive bacteria, archaea, and eukaryotes.
Function
Functionally-characterized members of the family appear to catalyze
The malaria parasite, Plasmodium falciparum, grows within its host erythrocyte and induces an increase in the permeability of the erythrocyte membrane to a range of solutes including Na+ and K+. This results in a progressive increase in the concentration of Na+ in the erythrocyte cytosol. The parasite cytosol has a relatively low Na+ concentration, generating a large inward Na+ gradient across the parasite plasma membrane. Saliba et al. (2006) showed that the parasite exploits the Na+ electrochemical gradient to energize the uptake of inorganic phosphate (Pi) with a stoichiometry of 2Na+:1Pi and with an apparent preference for the monovalent over the divalent form of Pi (see TC #2.A.20.2.5).
The generalized transport reactions possibly catalyzed by members of the PiT family are:
- HPO2−
4 (out) + [nH+ or Na+] (out) → HPO2−
4 (in) + [nH+ or Na+] (in) - Me2+ · HPO2−
4 (out) + nH+ (out) → Me2+ · HPO2−
4 (in) + nH+ (in) - SO2−
4 (out) + nH+ (out) → SO2−
4 (in) + nH+ (in).
Structure
The molecular sizes of Pit family members are reported to vary from 354 to 681 residues (10-12 TMSs) with the mammalian and Plasmodium proteins exhibiting the largest sizes. The sulfate permease of B. subtilis, CysP, is of 354 residues with 11 putative TMSs.[2] As of early 2016, it appears no crystal structures are available for PiT proteins.
Phylogeny
Phylogenetic grouping of the phosphate transport proteins generally correlates with organismal
Members of the PiT family arose by a tandem internal gene duplication event. Surprisingly, TopPred predicts a 12 TMS topology for the yeast Pho89 protein, but the homologous regions are not predicted to show similar topological features.[4][5]
See also
References
As of this edit, this article uses content from "2.A.20 The Inorganic Phosphate Transporter (PiT) Family", which is licensed in a way that permits reuse under the