Abstract:
:The Leishmania major aquaglyceroporin, LmAQP1, is responsible for the transport of antimonite [Sb(III)], an activated form of Pentostam or Glucantime. Downregulation of LmAQP1 provides resistance to trivalent antimony compounds and increased expression of LmAQP1 in drug-resistant parasites can reverse the resistance. Besides metalloid transport, LmAQP1 is also permeable to water, glycerol, methylglyoxal, dihydroxyacetone and sugar alcohols. LmAQP1 also plays a physiological role in volume regulation and osmotaxis. In this study, we examined the role of extracellular C-loop glutamates (Glu143, Glu145 and Glu152) in LmAQP1 activity. Alteration of both Glu143 and Glu145 to alanines did not affect either the biochemical or physiological properties of the protein, suggesting that neither residue is critical for LmAQP1 activity. Alteration of Glu152 to alanine, aspartate and glutamine affected metalloid transport in the order, wild-type > E152Q > E152D > E152A. In fact, axenic amastigotes expressing E152A LmAQP1 accumulated negligible levels of either arsenite [As(III)] or Sb(III). Alteration of Glu152 significantly affected volume regulation and osmotaxis, suggesting that Glu152 is critical for the physiological activity of the parasite. More importantly, alteration of Glu152 to alanine did not affect glycerol permeability. Although the metalloids, As(III) and Sb(III), are believed to be transported through aquaglyceroporin channels as they behave as inorganic molecular mimic of glycerol, this is the first report where metalloid and glycerol transport can be dissected by a single mutation at the extracellular pore entry of LmAQP1 channel.
journal_name
Mol Microbioljournal_title
Molecular microbiologyauthors
Uzcategui NL,Zhou Y,Figarella K,Ye J,Mukhopadhyay R,Bhattacharjee Hdoi
10.1111/j.1365-2958.2008.06494.xsubject
Has Abstractpub_date
2008-12-01 00:00:00pages
1477-86issue
6eissn
0950-382Xissn
1365-2958pii
MMI6494journal_volume
70pub_type
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