CHARACTERIZATION OF A GLUTAMINE-RICH AND PROLINE-RICH PROTEIN (QP PROTEIN) FROM THEILERIA-PARVA

We have isolated a clone from a Theileria parva infected lymphocyte cD NA library which has the potential to encode a protein of 480 amino ac ids. This protein is particularly rich in glutamine and proline and ha s some short repeated amino acid motifs based on the sequences QPXP an d QPXQ. We have called it the 'QP protein'. Southern blotting suggests that the QP protein gene is present as a single copy in the T. parva Muguga genome. Northern blotting revealed that the gene is transcribed in both schizonts and piroplasms. We have expressed part of the QP pr otein as a fusion with glutathione S-transferase in Escherichia coli a nd used this product to raise an anti-QP protein serum. Western blots of T. parva lysates using this serum showed a major polypeptide of app roximately 100 kDa and two further polypeptides of approximately 67 an d 72 kDa. Indirect immunofluorescence assays using the anti-QP protein serum on infected cells showed that the protein is associated with th e schizont. The pattern of staining in the indirect immunofluorescence assays and the structure of the protein suggest that it is a componen t of the schizont membrane.