MBIO 4600 Lecture Notes - Lecture 16: Ethyl Methanesulfonate, Chloromethane, Dna Mismatch Repair
25 Dec 2015
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Document Summary
Add alkyl groups (ch3, ch3ch2, etc. ) to bases or phosphates in. Some agents are naturally produced: e. g. marine algae (methyl chloride, s-adenosylmethionine, methylurea) Mutagens, carcinogens, and chemotherapeutic agents: direct and indirect alkylation. E. g. ethyl methanesulfonate (ems: n7 of guanine n7-methylguanine, n3 of adenine n3-methyladenine, base pair mismatches causing distortions in the helix. E. g. nitrosoguanidine: o6 of guanine o6-methylguanine, o4 of thymine o4-methylthymine, base pair mismatch but insignificant distortion of helix (cid:1) N-glycosylases in e. coli: taga (three methyladenine glycosylase a) (more specific) Removes 3-methyladenine and some related methylated and ethylated bases. Removes 3-methyladenine, 3-methylguanine, and 7: alka (less specific) methyl guanine, mechanism. Apurinic or apyrimidinic strand cut by ap endonuclease; exonuclease degradation. Methyltransferase: repair damage; not dna synthesis involved, remove alkyl group to themselves inactivated form degraded, in e. coli, ada and ogt (a. k. a. alkyltransferase i and ii) Repair alkylation of the o6 carbon of guanine and o4 carbon of thymine.
