[Bacteriophage Mu transposase contains a fragment with primary structure similar to that of protein VPg covalently linked with poliovirus RNA].

A statistically valid similarity was found to exist between the amino acid sequences of poliovirus genome-linked protein VPg and a fragment of bacteriophage Mu transposase (Mu A protein). Based on this observation a hypothesis is proposed that the molecular mechanisms underlying the functions of the two proteins may be analogous. Both proteins are supposed to be site-specific endonucleases which form covalent linkage with the 5'-phosphate group of the nicked DNA or RNA strand. The amino acid residue participating in the formation of this linkage in MuA is tentatively identified as Tyr413.