A long-range mutation affects conformational integrity and binding in RNase A
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The mutation induces major repositioning of the purine ligand but not pyrimidine
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Enhanced dynamics in distal regions are observed on the catalytic timescale
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Significant enhancement in loop dynamics induces major ligand repositioning
Summary
The role of internal dynamics in enzyme function is highly debated. Specifically, how small changes in structure far away from the reaction site alter protein dynamics and overall enzyme mechanisms is of wide interest in protein engineering. Using RNase A as a model, we demonstrate that elimination of a single methyl group located >10 Å away from the reaction site significantly alters conformational integrity and binding properties of the enzyme. This A109G mutation does not perturb structure or thermodynamic stability, both in the apo and ligand-bound states. However, significant enhancement in conformational dynamics was observed for the bound variant, as probed over nano- to millisecond timescales, resulting in major ligand repositioning. These results illustrate the large effects caused by small changes in structure on long-range conformational dynamics and ligand specificities within proteins, further supporting the importance of preserving wild-type dynamics in enzyme systems that rely on flexibility for function.
Present address: Department of Biochemistry and Molecular Biology, Edward A. Doisy Research Center, St. Louis University, 1100 South Grand Boulevard, St. Louis, MO 63103, USA
