Capping interactions in isolated alpha helices: position-dependent substitution effects and structure of a serine-capped peptide helix.
Capping interactions in isolated alpha helices: position-dependent substitution effects and structure of a serine-capped peptide helix.
复制标题
孤立的α螺旋中的加帽相互作用：位置依赖性取代效应和丝氨酸加帽的肽螺旋的结构。
DOI：
10.1021/bi00053a006
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发表时间：
1993
期刊：
影响因子：
2.9
通讯作者：
Kallenbach,NR
中科院分区：
文献类型：
--
作者：
Lyu,PC;Wemmer,DE;Zhou,HX;Pinker,RJ;Kallenbach,NR
Revised Manuscript Received October 20, 1992 abstract: The influence of an amino acid on the stability of a-helicalstructure depends on the position of the residue in the helix with respect to the ends. Short a helices in proteins are stabilized both by H-bonding of the main-chain NH and CO groups and by capping interactions between side chains and unfulfilled peptide groups at the N and C termini. Peptide models based on consensus position-dependent helix sequences allow one to model capping effects in isolated helices and to establish a base line for these interactions in proteins. We report here an extended series of substitutions in the cap positions of our peptide models and the solution structure of peptide S3, with serine at the N-cap position defined as the N-terminal residue with partly helix and partly coil conformation. The resulting model, determined by 2D'H NMR, is consistent with a structure at the N-cap involving H-bonding between the serine y oxygen and the peptide NH of the glutamic acid residue three amino acids toward the C terminus. A bifurcated H-bond of Ser 07 with the NH of Asp5 is possible also, since this group is within interacting distance. This provides direct evidence that specificside-chain interactions with the main chain stabilize isolated a-helical structure. a helices are among the most common secondary structures in proteins (Levitt, 1978; Fasman, 1989), for reasons that remain imperfectly understood. Side chains such as alanine and leucine tend tooccur frequently in the sequences of helices, while otherssuch as glycine do not. Differences amongside chains in their helix-stabilizing propensity have been dem-onstrated using synthetic model peptides (O’Neil & DeGrado, 1990; Lyu et al., 1990; Padmanabhan et al., 1990). Studies with synthetic polypeptide models havealso shown differences in helical propensities of natural amino acid guests but give different numerical values (Sueki et al., 1984), as discussed by Ptitsyn (1992). In contrast to the high molecular weight helical polypeptides that were used originally to analyze helix-coil transitions and determinehelix propensities (Bychkova et al., 1971; Barskaya & Ptitsyn, 1971; Sueki et al., 1984), the a helices in globularproteins are short, averaging only about 12 residues in length (Presta & Rose, 1988). The effect of the ends in helices of this length is therefore significant, because the H-bonding potential of four residues at the N and C termini cannot be satisfied by the main-chain CO (i)-NH-(j+ 4) hydrogen-bonding pattern characteristic of residues in the helix “middle”(Pauling & Corey, 1951; Presta & Rose, 1988). It follows that the mid-helix propensities now available (O’Neil & DeGrado, 1990; Lyu et al., 1990; Padmanabhan et al., 1990) apply strictly to a limited number of positions in protein helices.
