Purification and properties of a novel DNA methyltransferase from cultured rice cells.
DNA methyltransferase activity has been observed in a total crude homogenate of rice cells grown in suspension culture using either native plant DNA or, under the conditions used, the more responsive hemimethylated poly (dI-MedC).poly(dI-dC). Using the latter substrate we have purified an enzyme fraction 380-fold by salt extraction of chromatin, DEAE cellulose and phosphocellulose. This purified fraction showed enzyme activity only with poly (dI-MedC).poly(dI-dC) thus suggesting the occurrence in plants of a DNA methyltransferase specific for hemimethylated DNA. A Mr value of 54000 was calculated on the basis of the sedimentation coefficient which was determined by sucrose density gradient centrifugation. Apparent Km values for poly (dI-MedC).poly(dI-dC) and S-adenosyl-L-methionine were found to be 17 micrograms/ml and 2.6 microM, respectively.
Giordano
M
M
Dipartimento di Genetica e Microbiologia, Università di Pavia, Italy.
Mattachini
M E
ME
Cella
R
R
Pedrali-Noy
G
G
D002478:Cells, Cultured; D002499:Centrifugation, Density Gradient; D002843:Chromatin / Q000201:enzymology; D002852:Chromatography, Ion Exchange; D015254:DNA Modification Methylases / Q000737:chemistry / Q000302:isolation & purification*; D004795:Enzyme Stability; D007700:Kinetics; D012275:Oryza / Q000201:enzymology*; D011089:Polydeoxyribonucleotides / Q000378:metabolism; D012436:S-Adenosylmethionine / Q000378:metabolism; D013379:Substrate Specificity
D002843:Chromatin; D011089:Polydeoxyribonucleotides; D012436:S-Adenosylmethionine; D015254:DNA Modification Methylases