Enzymatic mechanism and product specificity of SET-domain protein lysine methyltransferases.
Molecular dynamics and hybrid quantum mechanics/molecular mechanics have been used to investigate the mechanisms of (+)AdoMet methylation of protein-Lys-NH(2) catalyzed by the lysine methyltransferase enzymes: histone lysine monomethyltransferase SET7/9, Rubisco large-subunit dimethyltransferase, viral histone lysine trimethyltransferase, and the Tyr245Phe mutation of SET7/9. At neutrality in aqueous solution, primary amines are protonated. The enzyme reacts with Lys-NH(3)(+) and (+)AdoMet species to provide an Enz.Lys-NH(3)(+).(+)AdoMet complex. The close positioning of two positive charges lowers the pK(a) of the Lys-NH(3)(+) entity, a water channel appears, and the proton escapes to the aqueous solvent; then the reaction Enz.Lys-NH(2).(+)AdoMet --> Enz.Lys-N(Me)H(2)(+).AdoHcy occurs. Repeat of the sequence provides dimethylated lysine, and another repeat yields a trimethylated lysine. The sequence is halted at monomethylation when the conformation of the Enz.Lys-N(Me)H(2)(+).(+)AdoMet has the methyl positioned to block formation of a water channel. The sequence of reactions stops at dimethylation if the conformation of Enz.Lys-N(Me)(2)H(+).(+)AdoMet has a methyl in position, which forbids the formation of the water channel.
Zhang
Xiaodong
X
Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, USA.
Bruice
Thomas C
TC
D002843:Chromatin; D011495:Histone-Lysine N-Methyltransferase / Q000737:chemistry / Q000378:metabolism*; D008239:Lysine; D008745:Methylation; D008958:Models, Molecular; D011789:Quantum Theory; D012435:S-Adenosylhomocysteine; D012436:S-Adenosylmethionine
D002843:Chromatin; D012436:S-Adenosylmethionine; D012435:S-Adenosylhomocysteine; D011495:Histone-Lysine N-Methyltransferase; D008239:Lysine