Cloning and structure-function analysis of the Leishmania donovani kinetoplastid membrane protein-11

Abstract

This report describes the complete translated gene sequence, predicted secondary structure and lipid bilayer association of a novel kinetoplastid membrane protein (KMP-11) from Leishmania donovani promastigotes. KMP-11 was previously referred to as the lipophosphoglycan-associated protein (LPGAP). The isolation, species distribution and chemical characterization, including a partial protein sequence analysis and post-translational modifications, of this major membrane component have been described [Jardim, Funk, Caprioli and Olafson (1995) Biochem. J. 305, 307-313]. C.d. measurements of KMP-11 indicated a very high helical content estimated to be approximately 86% in trifluoroethanol. This was in agreement with computer-based secondary-structure analyses which predicted KMP-11 to be almost exclusively alpha-helical, with the protein adopting a helix-loop-helix motif. Arrangement of the residues located in the putative helical regions on an Edmundson helical wheel showed that this molecule could have a strongly amphipathic conformation and provided an explanation for how such a highly charged protein might be inserted into the plasma membrane. Evidence in support of KMP-11 association with lipid bilayers was provided by showing that KMP-11 could mediate carboxyfluorescein release from liposomes. These findings suggested that KMP-11 may function in part to increase bilayer pressure, stabilizing molecules such as lipophosphoglycan within the parasite pellicular membrane.