Nature and distribution of sites of temperature-sensitive folding mutations in the gene for the P22 tailspike polypeptide chain.
Nature and distribution of sites of temperature-sensitive folding mutations in the gene for the P22 tailspike polypeptide chain.
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P22 尾尖多肽链基因中温度敏感折叠突变位点的性质和分布。
DOI：
10.1016/0022-2836(88)90359-2
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发表时间：
1988
影响因子：
5.6
通讯作者：
King,J
中科院分区：
文献类型：
--
作者：
Villafane,R;King,J
噬菌体P22基因9的温度敏感折叠（tsf）突变在限制性温度下干扰尾穗多肽链的折叠和结合。我们在此报告了24个独立突变体的位置和氨基酸替换。这些和先前确定的突变的分布明显是非随机的；所有32个突变位点都位于666个残基尾穗多肽链的中间350个残基上。n端140个氨基酸未发现突变，c端170个氨基酸未发现突变。由于这些突变体的生理缺陷是折叠途径中早期中间体的不稳定，突变体的定位表明，该链的中心区域对这种早期中间体的形成或稳定至关重要。大多数作为突变位点的氨基酸都是亲水性残基。这些残基的60%的替换代表电荷的变化。这可能反映了对成熟蛋白表面突变位点的选择，在那里替代可以最好地耐受而不干扰功能。突变位点均不在芳香残基上，仅发现一个脯氨酸位点。在这些残基上的替换可能导致致命的折叠缺陷，而这些缺陷在突变体中是无法恢复的。局部序列位于与回合报道相似的位点。结构研究确定β-薄片为主要的二级结构。这些突变可能会破坏β-片重复构象特征的形成，如旋转、链对之间的关联或片/片包装相互作用。这样的模型解释了在基因链的多个位置发生的具有相似缺陷表型的突变。
Temperature-sensitive folding (tsf) mutations in gene 9 of bacteriophage P22 interfere with the folding and association of the tailspike polypeptide chain at restrictive temperature. We report here the location and amino acid substitutions for 24 independenttsfmutants. The distribution of these and previously identified mutations is distinctly non-random; all of the 32 unambiguous sites oftsfmutations are located in the central 350 residues of the 666 residue tailspike polypeptide chain. Notsmutation has been found among the N-terminal 140 amino acids, and none among the C-terminal 170 amino acids. Since the physiological defect in these mutants is the destabilization of an early intermediate in the folding pathway, the localization of the mutants suggests that the central region of the chain is critical for formation or stabilization of this early intermediate.The majority of amino acids that served as sites for thetsfmutations were hydrophilic residues. Sixty percent of the replacements of these residues represented charge changes. This probably reflects the selection for mutant sites at the mature protein surface where the substitutions can be best tolerated without interfering with function. None of the sites oftsfmutations were at aromatic residues, and only one proline site was found. Substitutions at these residues may cause lethal folding defects which are not recovered astsfmutants.The local sequences attsfsites resemble those reported for turns. Structural studies identify β-sheet as the dominant secondary structure. These mutations may disrupt the formation of conformational features of β-sheets which are repeated, such as turns, associations between pairs of strands, or sheet/sheet packing interactions. Such a model accounts for the occurrence oftsfmutations with similar defective phenotypes at multiple positions along the chain.