Encinar J A, Fernández A M, Poveda J A, Molina M L, Albar J P, Gavilanes F, Gonzalez-Ros J M
Instituto de Biologia Molecular y Celular, Universidad Miguel Hernández, Elche, 03202 Alicante, Spain.
Biochemistry. 2003 Jul 29;42(29):8879-84. doi: 10.1021/bi0343121.
A synthetic peptide patterned after the sequence of the inactivating ball domain of the Shaker B K(+) channel, the ShB peptide, fully restores fast inactivation in the deletion Shaker BDelta6-46 K(+) channel, which lacks the constitutive ball domains. On the contrary, a similar peptide in which tyrosine 8 is substituted by the secondary structure-disrupting d-tyrosine stereoisomer does not. This suggests that the stereoisomeric substitution prevents the peptide from adopting a structured conformation when bound to the channel during inactivation. Moreover, characteristic in vitro features of the wild-type ShB peptide such as the marked propensity to adopt an intramolecular beta-hairpin structure when challenged by anionic phospholipid vesicles, a model target mimicking features of the inactivation site in the channel protein, or to insert into their hydrophobic bilayers, are lost in the d-tyrosine-containing peptide, whose behavior is practically identical to that of noninactivating peptide mutants. In the absence of high resolution crystallographic data on the inactivated channel/peptide complex, these latter findings suggest that the structured conformation required for the peptide to promote channel inactivation, as referred to above, is likely to be beta-hairpin.
一种模仿Shaker B钾离子通道失活球结构域序列合成的肽段（ShB肽），能完全恢复缺失组成型球结构域的缺失型Shaker BDelta6 - 46钾离子通道的快速失活功能。相反，一种将酪氨酸8替换为破坏二级结构的d - 酪氨酸立体异构体的类似肽段则不能恢复该功能。这表明这种立体异构取代阻止了肽段在失活过程中与通道结合时形成结构化构象。此外，野生型ShB肽的一些典型体外特征，比如当受到阴离子磷脂囊泡（一种模拟通道蛋白失活位点特征的模型靶点）挑战时显著倾向于形成分子内β - 发夹结构，或者插入其疏水双层膜，在含d - 酪氨酸的肽段中都消失了，该含d - 酪氨酸肽段的行为与非失活肽突变体几乎相同。在缺乏关于失活通道/肽复合物的高分辨率晶体学数据的情况下，这些最新发现表明，如上文所述，肽段促进通道失活所需的结构化构象可能是β - 发夹结构。
