CLONING AND STRUCTURE-FUNCTION ANALYSIS OF THE LEISHMANIA-DONOVANI KINETOPLASTID, MEMBRANE PROTEIN-11

This report describes-the complete translated gene sequence, predicted secondary structure and lipid bilayer association of a novel kinetopl astid membrane protein (KMP-11) from Leishmania donovani promastigotes . KMP-11 was previously referred to as the lipophosphoglycan-associate d protein (LPGAP). The isolation, species distribution and chemical ch aracterization, including a partial protein sequence analysis and post -translational modifications, of this major membrane component have be en described [Jardim, Funk, Caprioli and Olafson (1995) Biochem. J. 30 5, 307-313]. C.d. measurements of KMP-11 indicated a very high helical content estimated to be approximately 86% in trifluoroethanol. This w as in agreement with computer-based secondary-structure analyses which predicted KMP-11 to be almost exclusively a-helical, with the protein adopting a helix-loop-helix motif. Arrangement of the residues locate d 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 b e inserted into the plasma membrane. Evidence in support of KMP-11 ass ociation with lipid bilayers was provided by showing that KMP-11 could mediate carboxyfluorescein release from liposomes. These findings sug gested that KMP-11 may function in part to increase bilayer pressure, stabilizing molecules such as lipophosphoglycan within the parasite pe llicular membrane.