Peptide models of protein folding initiation sites. 2. The G-H turn region of myoglobin acts as a helix stop signal.
Peptide models of protein folding initiation sites. 2. The G-H turn region of myoglobin acts as a helix stop signal.
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蛋白质折叠起始位点的肽模型。
DOI：
10.1021/bi00076a007
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发表时间：
1993
期刊：
影响因子：
2.9
通讯作者：
Dyson,HJ
中科院分区：
文献类型：
--
作者：
Shin,HC;Merutka,G;Waltho,JP;Wright,PE;Dyson,HJ
1993年4月2日收到的修订稿摘要：合成了一系列抹香鲸肌红蛋白的多肽片段，对应于蛋白质的G-螺旋和H-螺旋之间的区段，并在水溶液和含水和三氟乙醇的混合溶剂中用圆二色谱和核磁共振研究了它们的构象偏好。最小的片段Mb-GH5是一个五个残基的多肽，其序列HPGDF对应于折叠蛋白中两个螺旋之间的连接环，在水溶液中采用高度布居的TURN构象。一个25个残基的多肽Mb-GH25含有相同的序列，两侧是G-和H-螺旋序列的连续片段，也发现该区域含有高比例的转角异构体。在水溶液中的侧翼序列中，无论是在Mb-GH25中还是在对照10个残基的多肽(Mb-Glo和Mb-HIO)中都没有观察到螺旋的形成，其序列对应于G-螺旋和H-螺旋片段。Mb-GH25在水溶液中没有观察到高于各组分之和的额外螺旋度，表明单体多肽在水溶液中没有形成螺旋发夹结构。在TFe存在的情况下，CD谱表明Mb-GH25中形成了有序的螺旋，核磁共振谱表明该螺旋位于多肽的N-末端。NOESY谱清楚地表明，在这些条件下，TURN的构象保持不变。在TFE存在的情况下，CD谱发现转角中心的Pro-Gly序列被Ala-Ala取代的多肽Mb-AA25含有明显更多的螺旋，表明在这种条件下，该转角序列在G-螺旋的C-末端起到螺旋停止信号的作用。TFE对这些多肽的构象偏好的影响证实，只有在具有高螺旋形成倾向的序列中才能诱导螺旋-对转角构象没有影响。这些结果表明，在折叠的初始阶段以及在天然蛋白质中，TURN序列对于螺旋终止可能是重要的。
Revised Manuscript Received April 2, 1993 abstract: A series of peptide fragments of sperm whale myoglobin, corresponding to segments of the region between the G-and H-helices of the protein, havebeen synthesized and their conformational preferences investigated using circular dichroism and nuclear magnetic resonance spectroscopy in aqueous solution and in solvent mixtures containing water and trifluoroethanol. The smallest fragment, Mb-GH5, a five-residue peptide with the sequence HPGDF corresponding to the connecting loop between the two helices in the folded protein, adopts highly populated turn conformations in aqueous solution. A 25-residue peptide, Mb-GH25, containing the same sequence flanked by contiguoussegments of the G-and H-helix sequences, was also found to contain a high proportion of conformers with a turn in this region. No helix formation was observed in the flanking sequences in water solution, either in Mb-GH25 or in control 10-residue peptides (Mb-GlO and Mb-HIO) with sequences corresponding to the G-and H-helix segments. No additional helicity above that of the sum of the components was observed for Mb-GH25, indicating that a helical hairpin structure is not formedin the monomeric peptide in aqueous solution. In the presence of TFE, ordered helix is formed in Mb-GH25 according to the CD spectrum, and NMR spectra indicatethat this is localized in the N-terminal portion of the peptide. NOESY spectra clearly show that theturn conformation is retained under these conditions. A peptide, Mb-AA25, inwhich the central Pro-Gly sequence of the turn are replaced with Ala-Ala was found to contain significantly more helix by CD in the presence of TFE, indicating that the turn sequence acts as a helix stop signal at the C-terminus of the G-helix under these conditions. The effect of TFE on the conformational preferences of these peptides confirms that helix is induced only in sequences which have a high propensity for helix formation—there is no effect on the turn conformation. These results suggest that the turn sequence may be important for helix termination during the initial stages of folding as well as in the native protein.
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影响因子：
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作者：
T. Takano
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DOI：
--
发表时间：
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影响因子：
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影响因子：
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作者：
Wright,PE;Dyson,HJ;Lerner,RA
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