A single amino acid change restores DNA cytosine methyltransferase activity in a cloned chlorella virus pseudogene. |
| |
| Authors: | Y Zhang M Nelson and J L Van Etten |
| |
| Institution: | Department of Plant Pathology, University of Nebraska, Lincoln 68583-0722. |
| |
| Abstract: | 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.CviJI, encoded by a different chlorella virus IL-3A. Whereas IL-3A expresses M.CviJI, 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.CviJI and site-directed point mutations revealed that changing Gln188 to Lys188 abolishes M.CviJI methyltransferase activity. Conversely, changing Lys188 in P17-ORF4 to Gln188 results in M.CviJI activity. The other altered seven amino acids do not appear to affect M.CviJI activity. |
| |
| Keywords: | |
|
|
