Effect of an Imposed Contact on Secondary Structure in the Denatured State of Yeast Iso-1-cytochrome c.
Effect of an Imposed Contact on Secondary Structure in the Denatured State of Yeast Iso-1-cytochrome c.
复制标题
强加接触对变性状态下酵母 Iso-1-细胞色素 c 二级结构的影响。
DOI：
10.1021/acs.biochem.7b01002
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发表时间：
2017
期刊：
影响因子：
2.9
通讯作者：
Bowler,BruceE
中科院分区：
文献类型：
--
作者：
Danielson,TravisA;Stine,JessicaM;Dar,TanveerA;Briknarova,Klara;Bowler,BruceE
There is considerable evidence that long-range interactions stabilize residual protein structure under denaturing conditions. However, evaluation of the effect of a specific contact on structure in the denatured state has been difficult. Iso-1-cytochromecvariants with a Lys54 → His mutation form a particularly stable His–heme loop in the denatured state, suggestive of loop-induced residual structure. We have used multidimensional nuclear magnetic resonance methods to assign1H and15N backbone amide and13C backbone and side chain chemical shifts in the denatured state of iso-1-cytochromeccarrying the Lys54 → His mutation in 3 and 6 M guanidine hydrochloride and at both pH 6.4, where the His54–heme loop is formed, and pH 3.6, where the His54–heme loop is broken. Using the secondary structure propensity score, with the 6 M guanidine hydrochloride chemical shift data as a random coil reference state for data collected in 3 M guanidine hydrochloride, we found residual helical structure in the denatured state for the 60s helix and the C-terminal helix, but not in the N-terminal helix in the presence or absence of the His54–heme loop. Non-native helical structure is observed in two regions that form Ω-loops in the native state. There is more residual helical structure in the C-terminal helix at pH 6.4 when the loop is formed. Loop formation also appears to stabilize helical structure near His54, consistent with induction of helical structure observed when His–heme bonds form in heme–peptide model systems. The results are discussed in the context of the folding mechanism of cytochromec.
