THE TRYPANOSOMA-BRUCEI AUTOANTIGEN I 6 IS AN INTERNALLY REPETITIVE CYTOSKELETAL PROTEIN/

Self-reactive host antibodies were shown earlier to exhibit strong and specific cross-reactivity to a particular trypanosomal antigen, prote in I/6. The current study presents the molecular characterization of p rotein I/6. The major structural component of the cell body cytoskelet on of Trypanosoma brucei is a cagelike array of tightly connected micr otubules which is in close contact to the overlaying cell membrane. Ma ny of the unususal properties of the cytoskeleton of trypanosomes are due to the proteins associated with these microtubules. Protein I/6 wa s now shown to be a microtubule-associated protein, and it may be invo lved in crosslinking microtubules. Protein I/6 is coded for by a singl e gene, representing an exception rather than tile rule for trypanosom al gene organization. From this single gene, two distinct mRNAs are ge nerated through differential splicing. They differ in their polyadenyl ation sites, but both code for an identical polypeptide sequence of 33 kDa, Protein I/6 contains a non-functional EF-hand calcium binding do main and a domain of six tandemly arranged repeat units of eight amino acids length.