title: Nucleoside and nucleotide inactivation of R17 coat protein: evidence for a transient covalent RNA-protein bond.
abstract: R17 coat protein forms a specific complex with a 21-nucleotide RNA hairpin containing the initiation site for the phage replicase gene. The RNA binding activity of the protein is inhibited by prior incubation with 5-bromouridine (BrU). The inactivation occurs with pseudo-first-order kinetics, and the inactive protein is stable to dilution. RNA binding activity of the BrU-inactivated protein is restored upon incubation with dithiothreitol. Inactivation of coat protein by N-ethylmaleimide or p-(chloromercuri)-benzenesulfonate indicates that a cysteine residue is located near the RNA binding site. Since 5-bromodeoxyuridine does not inactivate coat protein, a specific binding event appears to be required before inactivation can occur. Surprisingly, unmodified cytidine nucleotides also inactivate coat protein, with a specificity similar to the modified analogues. These results are discussed with regard to the formation of a transient covalent RNA-protein bond.
mesh_terms: D002213:Capsid / Q000378:metabolism*; D036022:Capsid Proteins; D002729:Chloromercuribenzoates / Q000494:pharmacology; D003090:Coliphages / Q000378:metabolism*; D005033:Ethylmaleimide / Q000494:pharmacology; D007700:Kinetics; D012343:RNA, Transfer / Q000378:metabolism*; D016601:RNA-Binding Proteins; D012263:Ribonucleosides / Q000494:pharmacology*; D012265:Ribonucleotides / Q000494:pharmacology*; D013329:Structure-Activity Relationship; D020245:p-Chloromercuribenzoic Acid
chemical_list: D036022:Capsid Proteins; D002729:Chloromercuribenzoates; D016601:RNA-Binding Proteins; D012263:Ribonucleosides; D012265:Ribonucleotides; D020245:p-Chloromercuribenzoic Acid; D012343:RNA, Transfer; D005033:Ethylmaleimide