Kiyokawa T, Kanaori K, Tajima K, Tanaka T
Department of Applied Biology, Kyoto Institute of Technology, Matugasaki, Sakyou-ku, Kyoto 606-8585, Japan.
Biopolymers. 2000;55(5):407-14. doi: 10.1002/1097-0282(2000)55:5<407::AID-BIP1015>3.0.CO;2-Y.
The amino acid sequence that forms the alpha-helical coiled coil structure has a representative heptad repeat denoted by defgabc, according to their positions. Although the a and d positions are usually occupied by hydrophobic residues, hydrophilic residues at these positions sometimes play important roles in natural proteins. We have manipulated a few amino acids at the a and d positions of a de novo designed trimeric coiled coil to confer new functions to the peptides. The IZ peptide, which has four heptad repeats and forms a parallel triple-stranded coiled coil, has Ile at all of the a and d positions. We show three examples: (1) the substitution of one Ile at either the a or d position with Glu caused the peptide to become pH sensitive; (2) the metal ion induced alpha-helical bundles were formed by substitutions with two His residues at the d and a positions for a medium metal ion, and with one Cys residue at the a position for a soft metal ion; and (3) the AAB-type heterotrimeric alpha-helical bundle formation was accomplished by a combination of Ala and Trp residues at the a positions of different peptide chains. Furthermore, we applied these procedures to prepare an ABC-type heterotrimeric alpha-helical bundle and a metal ion-induced heterotrimeric alpha-helical bundle.
形成α-螺旋卷曲螺旋结构的氨基酸序列具有一个代表性的七肽重复序列，根据其位置用defgabc表示。虽然a和d位置通常被疏水残基占据，但这些位置的亲水残基有时在天然蛋白质中发挥重要作用。我们在一个从头设计的三聚体卷曲螺旋的a和d位置操纵了几个氨基酸，以赋予肽新的功能。具有四个七肽重复序列并形成平行三链卷曲螺旋的IZ肽，在所有a和d位置都有Ile。我们展示三个例子：（1）在a或d位置将一个Ile替换为Glu会使肽对pH敏感；（2）对于中等金属离子，通过在d和a位置用两个His残基替换，以及对于软金属离子，在a位置用一个Cys残基替换，形成金属离子诱导的α-螺旋束；（3）通过在不同肽链的a位置组合Ala和Trp残基来完成AAB型异三聚体α-螺旋束的形成。此外，我们应用这些方法制备了ABC型异三聚体α-螺旋束和金属离子诱导的异三聚体α-螺旋束。
