The Baculovirus Autographa Californica Encodes a Protein Tyrosine Phosphatase

The genome of the baculovirus Autographa californica encodes a 19-kDa protein (BVP) containing an active site sequence motif ((I/V)HCXAGXXR(S/T)G) that characterizes a large family of protein tyrosine phosphatases (PTPs). The baculoviral protein was expressed in Escherichia coli and purified so that its enzymatic properties could be examined. We have demonstrated that recombinant BVP has intrinsic protein tyrosine phosphatase activity. Like VH1, a PTP encoded by vaccinia virus, BVP also dephosphorylates seryl or threonyl residues. However, the similarity of BVP to VH1 or the catalytic domains from PTPs of eukaryotic origin is restricted to a small region surrounding the active site motif. In contrast, the similarity of BVP to two putative PTPs encoded by the CDC14 gene of Saccharomyces cerevisiae and a gene of unknown function from Caenorhabditis elegans extends throughout its sequence. We postulate that BVP and its two homologs constitute a unique subfamily that may differ from other PTPs in having a specialized function, mode of regulation, or substrate preference.