MOLECULAR CHARACTERIZATION OF THE KINETOPLASTID MEMBRANE PROTEIN-II FROM AFRICAN TRYPANOSOMES

The kinetoplastid membrane protein-11 molecule was purified from Trypa nosoma brucei rhodesiense and an internal peptide sequence was obtaine d. This sequence information was used with cosmid library screening an d polymerase chain reaction amplifications of both genomic DNA and cDN A to obtain the entire DNA sequence of the encoding gene and the corre sponding translated amino acid sequence of 92 residues. The sequence s howed 18% divergence from the corresponding molecule of the related ki netoplastid Leishmania donovani, including one key amino acid at posit ion 45 which may be of functional relevance. The protein had a calcula ted molecular mass of 11 078 Da, a pi of 6.0 and an overall net charge of -2 at physiological pH. The secondary structure of the molecule wa s predicted to consist of two amphipathic helices connected by a rando m-coil segment, and suggests that it would interact with lipid bilayer s in the trypanosome cell membrane. Northern and Southern blot analyse s showed that the trypanosome kinetoplastid membrane protein-11 molecu le was translated from a single transcript and was transcribed from a single gene copy, thus making this molecule an attractive target for k nockout mutagenesis.