Hecht M H, Richardson J S, Richardson D C, Ogden R C
Department of Biochemistry, Duke University, Durham, NC 27710.
Science. 1990 Aug 24;249(4971):884-91. doi: 10.1126/science.2392678.
The protein Felix was designed de novo to fold into an antiparallel four-helix bundle of specific topology. Its sequence of 79 amino acid residues is not homologous to any known protein sequence, but is "native-like" in that it is nonrepetitive and contains 19 of the 20 naturally occurring amino acids. Felix has been expressed from a synthetic gene cloned in Escherichia coli, and the protein has been purified to homogeneity. Physical characterization of the purified protein indicates that Felix (i) is monomeric in solution, (ii) is predominantly alpha-helical, (iii) contains a designed intramolecular disulfide bond linking the first and fourth helices, and (iv) buries its single tryptophan in an apolar environment and probably in close proximity with the disulfide bond. These physical properties rule out several alternative structures and indicate that Felix indeed folds into approximately the designed three-dimensional structure.
蛋白质Felix是从头设计的，可折叠成具有特定拓扑结构的反平行四螺旋束。它由79个氨基酸残基组成的序列与任何已知蛋白质序列都不同源，但具有“天然样”特征，即它是非重复的，并且包含20种天然存在的氨基酸中的19种。Felix已通过克隆到大肠杆菌中的合成基因表达，并且该蛋白质已纯化至同质。纯化蛋白质的物理表征表明，Felix（i）在溶液中是单体，（ii）主要是α-螺旋，（iii）包含一个设计的分子内二硫键，连接第一和第四螺旋，并且（iv）将其单个色氨酸埋藏在非极性环境中，并且可能与二硫键紧密相邻。这些物理性质排除了几种替代结构，并表明Felix确实折叠成近似设计的三维结构。
