Vaccinia virus encodes an essential gene with strong homology to protein kinases.

The B1 gene of vaccinia virus encodes a 34-kDa protein which is essential for viral replication. Temperature-sensitive mutants bearing lesions in this gene arrest at the stage of DNA replication during nonpermissive infections. In this report, the sequence of the 34-kDa open reading frame is presented, and the mutations in two ts alleles are identified. Analysis of the deduced protein sequence reveals strong homology with catalytic domains of numerous protein kinases. The lesion in one of the mutants alters an invariant glycine residue within one such domain.