Evidence that the 'active centre' of the herpes simplex virus thymidine kinase involves an interaction between three distinct regions of the polypeptide.

The nucleotide sequence of the coding region of the thymidine kinase gene from each of three mutant strains of herpes simplex virus type 1 and from the parental strain, SC16, has been determined. The mutants were known to express thymidine kinase enzymes with distinct substrate binding properties. Consideration of the lesions in the genes responsible for these altered biochemical properties. Consideration of the lesions in the genes responsible for these altered biochemical properties has led us to postulate a preliminary model for the active centre of the enzyme, involving the cooperation of three distinct regions of the polypeptide.