title: Crosslinking of Dam methyltransferase with S-adenosyl-methionine.
abstract: Highly purified DNA-adenine methyltransferase was irradiated in the presence of different concentrations of radiolabelled S-adenosyl-methionine (AdoMet) with a conventional Mineralight UV-lamp from several minutes up to 1 h while incubating in ice. Incorporation of radioactivity was monitored by electrophoresis of the crosslink between S-adenosyl-methionine and Dam methylase on SDS-polyacrylamide gels followed by fluorography. Crosslinking reached a maximum in presence of 10 microM S-adenosyl-methionine; it was inhibited in the presence of substances which competitively inhibit methylation of DNA by Dam methylase, like sinefungin or S-adenosyl-homocysteine, but not in the presence of non-inhibitors like ATP or S-isobutyl-adenosine. The crosslink obtained was resistant against a wide range of even drastic conditions commonly used in protein and peptide chemistry. Proteins, which do not bind S-adenosyl-methionine, as well as heat inactivated Dam methylase were not photolabelled. After limited proteolysis the radioactive label appeared only in certain of the peptides obtained. From Western blots carried out with polyclonal antibodies produced against a synthetic peptide corresponding in its sequence to amino acids 92-106 of the Dam methylase, the crosslinking of AdoMet could be tentatively mapped at a position after amino acid 106.
authors.affiliation: Département de Biologie Moleculaire et Cellulaire, Centre d'Etudes Nucléaires de Saclay, Gif-sur-Yvette, France.
authors.forename: C
authors.initials: C
authors.lastname: Wenzel
authors.forename: M
authors.initials: M
authors.lastname: Moulard
authors.forename: A
authors.initials: A
authors.lastname: Løbner-Olesen
authors.forename: W
authors.initials: W
authors.lastname: Guschlbauer
mesh_terms: D001667:Binding, Competitive; D003432:Cross-Linking Reagents / Q000378:metabolism*; D010450:Endopeptidases / Q000494:pharmacology; D004789:Enzyme Activation; D004795:Enzyme Stability / Q000187:drug effects / Q000528:radiation effects; D006358:Hot Temperature; D008780:Methyltransferases / Q000378:metabolism*; D012436:S-Adenosylmethionine / Q000378:metabolism*; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); D013379:Substrate Specificity / Q000187:drug effects / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D003432:Cross-Linking Reagents; D012436:S-Adenosylmethionine; D008780:Methyltransferases; C058693:Dam methyltransferase; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); D010450:Endopeptidases