Mutagenesis of a stacking contact in the MS2 coat protein-RNA complex.
AUTOR(ES)
LeCuyer, K A
RESUMO
The thermodynamic contribution of a stacking interaction between Tyr85 in MS2 coat protein and a single-stranded pyrimidine in its RNA binding site has been examined. Mutation of Tyr85 to Phe, His, Cys, Ser and Ala decreased the RNA affinity by 1-3 kcal/mol under standard binding conditions. Since the Phe, His and Cys 85 proteins formed UV photocrosslinks with iodouracil-containing RNA at the same rate as the wild-type protein, the mutant proteins interact with RNA in a similar manner. The pH dependence of KD for the Phe and His proteins differs substantially from the wild-type protein, suggesting that the titration of position 85 contributes substantially to the binding properties. Experiments with specifically substituted phosphorothioate RNAs confirm a hydrogen bond between the hydroxyl group of tyrosine and a phosphate predicted by the crystal structure.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=452510Documentos Relacionados
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