四肽重复(TPR)结构域是普遍存在的蛋白质相互作用结构域,其采用α-螺旋的模块化反平行阵列。TPR折叠通常采用单体状态,和共有TPR序列成功折叠成预期的单体拓扑。TPR折叠的多功能性还支持不同的四元结构,它可以作为调节开关。一个例子是酵母线粒体裂变1(Fis1),它似乎在调节过氧化物酶体和线粒体的分裂中在单体和二聚体状态之间相互转化。人Fis1是否也可以像酵母分子一样相互转化是未知的。酵母分子中不存在人Fis1中的TPR共有脯氨酸残基,当添加时,防止酵母Fis1二聚化,表明TPR共有脯氨酸可能持续存在以防止TPR寡聚化。这里,我们用人类Fis1和共有TPR蛋白CTPR3来解决这个问题。我们证明人Fis1不通过其TPR结构域形成非共价二聚体,尽管条件有利于酵母蛋白质的二聚化。我们还表明,共有脯氨酸的存在不足以阻止TPR二聚化。最后,对所有可用的TPR蛋白结构的分析(22个非冗余结构,总共64个TPRs-42带有共有脯氨酸,22个没有)表明共有脯氨酸对于转弯形成不是必需的,但有利于更短的转弯。这项工作表明TPR共有脯氨酸不是为了防止寡聚化,而是为了支持重复之间的紧密转弯。
Tetratricopeptide repeat (TPR) domains are ubiquitous protein interaction domains that adopt a modular antiparallel array of α-helices. The TPR fold typically adopts a monomeric state, and
consensus TPRs sequences successfully fold into the expected monomeric topology. The versatility of the TPR fold also supports different quaternary structures, which may function as regulatory switches. One example is yeast mitochondrial fission 1 (Fis1) that appears to interconvert between monomer and dimer states in regulating division of peroxisomes and mitochondria. Whether human Fis1 can also interconvert like the yeast molecule is unknown. A TPR
consensus proline residue present in human Fis1 is absent in the yeast molecule and, when added, prevents yeast Fis1 dimerization suggesting that the TPR
consensus proline might have persisted to prevent TPR oligomerization. Here, we address this question with human Fis1 and the
consensus TPR protein CTPR3. We demonstrate that human Fis1 does not form a noncovalent dimer via its TPR domain, despite conditions that favor dimerization of the yeast protein. We also show that the presence of the
consensus proline is not sufficient to forbid TPR dimerization. Lastly, an analysis of all available TPR protein structures (22 nonredundant structures, totaling 64 TPRs-42 with the consensus proline and 22 without) revealed that the consensus proline is not necessary for turn formation, but does favor shorter turns. This work suggests the TPR consensus proline is not to prevent oligomerization, but to favor tight turns between repeats.