A single amino acid change restores DNA cytosine methyltransferase activity in cloned chlorella virus pseudogene
1992
Zhang, Y. | Nelson, M. | Van Ettern, J.L.
The chlorella virus PBCV-1 contains an open reading frame, named P17-ORF4, which differs by eight amino acids from a DNA cytosine methyltransferase, M.CviJl, encoded by a different chlorella virus lL-3A. Whereas lL-3A expresses M.CviJl, which methylates the central cytosine in (A/G)GC(T/C/G) sequences, P17-ORF4 is non-functional. Gene fusions between P17-ORF4 and M.CviJl and site-directed point mutations revealed that changing Gln188 to Lys188 abolishes M.CviJl methyltransferase activity. Conversely, changing Lys188 in P17-ORF4 to Gln188 results in M.CviJl activity. The other altered seven amino acids do not appear to affect M.CviJl activity.
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