We have studied the role of protein dynamics in chemical catalysis in the enzyme dihydrofolate reductase (DHFR), using a pump–probe method that employs pulsed-laser photothermal heating of a gold nanoparticle (AuNP) to directly excite a local region of the protein structure and transient absorbance to probe the effect on enzyme activity. Enzyme activity is accelerated by pulsed-laser excitation when the AuNP is attached close to a network of coupled motions in DHFR (on the FG loop, containing residues 116–132, or on a nearby alpha helix). No rate acceleration is observed when the AuNP is attached away from the network (distal mutant and His-tagged mutant) with pulsed excitation, or for any attachment site with continuous wave excitation. We interpret these results within an energy landscape model in which transient, site-specific addition of energy to the enzyme speeds up the search for reactive conformations by activating motions that facilitate this search.

我们研究了蛋白质动力学在二氢叶酸还原酶 (DHFR) 化学催化中的作用，使用泵探针方法，该方法采用金纳米颗粒 (AuNP) 的脉冲激光光热加热直接激发蛋白质结构的局部区域和瞬时吸光度以探测对酶活性的影响。当 AuNP 靠近 DHFR 中的耦合运动网络（在 FG 环上，包含残基 116-132，或在附近的 α 螺旋上）时，脉冲激光激发会加速酶活性。当 AuNP 以脉冲激发远离网络（远端突变体和 His 标记突变体）时，或对于任何具有连续波激发的附着位点，没有观察到速率加速。我们在能源景观模型中解释这些结果，其中瞬态，