Selective reaction of glyoxal with guanine residues in native and denatured Escherichia coli 5S RNA

Abstract

Summary The accessibility to glyoxal of guanine residues in various conformations of 5S RNA has been studied. While guanine at position 41 in the primary structure of 5S RNA is the most easily accessible in native RNA, guanines at positions 61, 100 and/or 102, readily react in the denatured B conformation obtained after exposure to urea and EDTA. Although heat denaturation has the same effect as urea-EDTA denaturation with regard to the electrophoretic mobility of 5S RNA on polyacrylamide gels, it does not significantly unmask residue G61. Native 5S RNA, specifically formylated at G41 by glyoxal and periodate treatment, displays good affinity for ribosomal proteins. The B-form, which is entirely devoid of affinity, recovers it after renaturation at 55o in the presence of Mg2+ ions. This recovery is completely prevented by blocking accessible G residues in the B-form by reaction with glyoxal and periodate.