Department of Chemistry, Emory University, Atlanta, GA 30322.
Department of Chemistry, Emory University, Atlanta, GA 30322
Proc Natl Acad Sci U S A. 2021 Jan 26;118(4). doi: 10.1073/pnas.2014592118.
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.
我们研究了在酶二氢叶酸还原酶 (DHFR) 中蛋白质动力学在化学催化中的作用，使用了一种泵浦探针方法，该方法利用金纳米粒子 (AuNP) 的脉冲激光光热加热来直接激发蛋白质结构的局部区域，并通过瞬态吸收来探测对酶活性的影响。当 AuNP 附着在 DHFR 的耦合运动网络附近时（在 FG 环上，包含残基 116-132，或附近的 alpha 螺旋上），酶活性会随着脉冲激光激发而加速。当 AuNP 远离网络（远侧突变体和 His 标记突变体）时，或者在任何附着位点用连续波激发时，都不会观察到速率加速。我们在能量景观模型中解释了这些结果，在该模型中，酶的瞬时、特定部位的能量增加通过激活促进这种搜索的运动，从而加速对反应构象的搜索。
