Identification and characterization of a novel 34 kDa merozoite protein in Babesia orientalis.

A novel Babesia orientalis 34 kDa protein (designated BoP34) was obtained by immunoscreening of a cDNA expression library using B. orientalis infected water buffalo serum. The complete nucleotide sequence of the BoP34 was 1088 bp, which contained one open reading frame (ORF), two untranslated regions (UTRs) and a poly (A) tail. The length of ORF was 933 bp, encoding a polypeptide of 310 aa with a predicted size of 34 kDa. BLAST analysis showed that the nucleotide sequence of BoP34 had 71% similarity with that of the Babesia bovis gene XM_001611335, which encodes a nuclear movement family protein. This suggested that BoP34 is a homologous of the movement family protein. Structural analysis of the BoP34 protein indicated a CS domain which may interact with the ATPase domain of the heat shock protein 90. A truncated version of BoP34 was cloned into the expression vector pET-32a and subsequently expressed and purified from the Escherichia coli Rosetta™ (DE3) pLysS stain as a Trx-fusion (designated rBoP34-T). Antibodies in the serum of a B. orientalis-infected water buffalo were able to recognize this protein in immune-bloting analysis. Rabbit antibodies raised against rBoP34-T could detecte native BoP34 (34 kDa) in B. orientalis-infected water buffalo erythrocytes. These results suggested that BoP34 might be a good diagnostic antigen for the specific detection of anti-B. orientalis antibody in water buffalo. Further research is required to explore the biological function and diagnostic potential of this molecule.