%0 Journal Article
%T Stereospecific removal of methyl phosphotriesters from DNA by an Escherichia coli ada+ extract.
%A Weinfeld M
%A Drake AF
%A Saunders JK
%A Paterson MC
%J Nucleic Acids Res
%V 13
%N 19
%D Oct 1985 11
%M 3903661
%F 19.16
%R 10.1093/nar/13.19.7067
%X The ada+ gene product, a DNA methyltransferase present in extracts from an Escherichia coli strain constitutive for the adaptive response, removes only half of the methyl phosphotriesters from alkylated DNA. Since DNA phosphotriesters occur in two isomeric configurations (denoted Rp and Sp), we examined whether this reflects a stereospecific mode of repair by the methyltransferase. Analysis by reverse-phase HPLC, phosphorus NMR and circular dichroism established that only triesters in the Sp configuration are acted upon by the E. coli extract.