IDENTIFICATION OF THE NICKING TYROSINE OF GEMINIVIRUS REP PROTEIN

The replication initiator (Rep) proteins of geminiviruses perform a DN A cleavage and strand transfer reaction at the viral origin of replica tion, As a reaction intermediate, Rep proteins become covalently linke d to the 5' end of the cleaved DNA, We have used tomato yellow leaf cu rl virus Rep protein for in vivo and in vitro analyses, Isolating a co valent peptide-nucleotide complex, we have identified the amino acid o f Rep which mediates cleavage and links the protein to DNA, We show th at tyrosine-103, located in a conserved sequence motif, initiates DNA cleavage and is the physical link between geminivirus Rep protein and its origin DNA.