Baryshnikova E N, Mel'nik B S, Katina N S, Finkel'shteĭn A V, Bychkova V E
Mol Biol (Mosk). 2009 Jan-Feb;43(1):136-47.
The effect of some amino acid residues in A, B, G, and H helices on the folding nucleus and folding intermediate state formation was estimated. For four apomyoglobin mutant forms with point replacements of hydrophobic amino acid residues by Ala, the influence of the substitutions on the stability of native (N) protein and its folding intermediate state (I) was studied, as well as on the protein folding/unfolding rates. Equilibrium and kinetic studies on mutant proteins over a wide range of urea concentrations have shown that the protein native state was strongly destabilized in comparison with that of the wild type protein. At the same time, stability of the intermediate state changed insignificantly. It was shown that amino acid residues of A, G, and H helices make a small contribution to apomyoglobin folding nucleus stabilization in the rate-limiting I reversible N transition, which occurred after the intermediate state was formed. But the amino acid residue of B-helix was very important for the folding nucleus stabilization in the transition state upon the I reversible N transition.
评估了A、B、G和H螺旋中一些氨基酸残基对折叠核和折叠中间体状态形成的影响。对于四种将疏水性氨基酸残基替换为丙氨酸的脱辅基肌红蛋白突变体形式，研究了这些替换对天然（N）蛋白及其折叠中间体状态（I）稳定性的影响，以及对蛋白质折叠/去折叠速率的影响。在广泛的尿素浓度范围内对突变蛋白进行的平衡和动力学研究表明，与野生型蛋白相比，突变蛋白的天然状态稳定性显著降低。同时，中间体状态的稳定性变化不明显。结果表明，在限速的I可逆N转变（发生在中间体状态形成之后）中，A、G和H螺旋的氨基酸残基对脱辅基肌红蛋白折叠核的稳定作用较小。但是，B螺旋的氨基酸残基在I可逆N转变的过渡态中对折叠核的稳定非常重要。
