Fernandez-Ballester G, Gavilanes F, Albar J P, Criado M, Ferragut J A, Gonzalez-Ros J M
Department of Neurochemistry, University of Alicante, Spain.
Biophys J. 1995 Mar;68(3):858-65. doi: 10.1016/S0006-3495(95)80262-6.
The conformation of the inactivating peptide of the Shaker B K+ channel (ShB peptide) and that of a noninactivating mutant (ShBL7E peptide) have been studied. Under all experimental conditions explored, the mutant peptide remains in a predominantly nonordered conformation. On the contrary, the inactivating ShB peptide has a great tendency to adopt a highly stable beta structure, particularly when challenged "in vitro" by anionic phospholipid vesicles. Because the putative peptide binding elements at the inner mouth of the channel comprise a ring of anionic residues and a hydrophobic pocket, we hypothesize that the conformational restrictions imposed on the ShB peptide by its interaction with the anionic lipid vesicles could partly imitate those imposed by the above ion channel elements. Thus, we propose that adoption of beta structure by the inactivating peptide may also occur during channel inactivation. Moreover, the difficulties encountered by the noninactivating ShBL7E peptide mutant to adopt beta structure and the observation that trypsin hydrolysis of the ShB peptide prevent both structure formation and channel inactivation lend further support to the hypothesis that adoption of beta structure by the inactivating peptide in a hydrophobic environment is important in determining channel blockade.
对Shaker B钾通道失活肽（ShB肽）和非失活突变体（ShBL7E肽）的构象进行了研究。在所探索的所有实验条件下，突变肽主要保持无序构象。相反，失活的ShB肽极易形成高度稳定的β结构，尤其是在“体外”受到阴离子磷脂囊泡作用时。由于通道内口假定的肽结合元件包括一圈阴离子残基和一个疏水口袋，我们推测，ShB肽与阴离子脂质囊泡相互作用对其构象的限制可能部分模拟了上述离子通道元件所施加的限制。因此，我们提出失活肽形成β结构的过程也可能发生在通道失活期间。此外，非失活的ShBL7E肽突变体难以形成β结构，以及观察到胰蛋白酶水解ShB肽会阻止结构形成和通道失活，这进一步支持了以下假设：在疏水环境中，失活肽形成β结构对于确定通道阻断很重要。
