Department of Chemistry, University of Naples Federico II, Complesso Universitario Monte S. Angelo, Via Cinthia, I-80126 Naples, Italy.
Biochimie. 2012 May;94(5):1108-18. doi: 10.1016/j.biochi.2012.01.010. Epub 2012 Jan 17.
3D domain swapping is the process by which two or more protein molecules exchange part of their structure to form intertwined dimers or higher oligomers. Bovine pancreatic ribonuclease (RNase A) is able to swap the N-terminal α-helix (residues 1-13) and/or the C-terminal β-strand (residues 116-124), thus forming a variety of oligomers, including two different dimers. Cis-trans isomerization of the Asn113-Pro114 peptide group was observed when the protein formed the C-terminal swapped dimer. To study the effect of the substitution of Pro114 on the swapping process of RNase A, we have prepared and characterized the P114A monomeric and dimeric variants of the enzyme. In contrast with previous reports, the crystal structure and NMR data on the monomer reveals a mixed cis-trans conformation for the Asn113-Ala114 peptide group, whereas the X-ray structure of the C-terminal swapped dimer of the variant is very close to that of the corresponding dimer of RNase A. The mutation at the C-terminus affects the capability of the N-terminal α-helix to swap and the stability of both dimeric forms. The present results underscore the importance of the hydration shell in determining the cross-talk between the chain termini in the swapping process of RNase A.
3D 结构域交换是指两个或多个蛋白质分子交换部分结构以形成交错二聚体或更高寡聚体的过程。牛胰核糖核酸酶（RNase A）能够交换 N 端α-螺旋（残基 1-13）和/或 C 端β-折叠（残基 116-124），从而形成各种寡聚体，包括两种不同的二聚体。当蛋白质形成 C 端交换二聚体时，观察到 Asn113-Pro114 肽基团的顺反异构化。为了研究 Pro114 取代对 RNase A 交换过程的影响，我们已经制备和表征了该酶的 P114A 单体和二聚体变体。与以前的报告相反，单体的晶体结构和 NMR 数据揭示了 Asn113-Ala114 肽基团的混合顺反构象，而变体的 C 端交换二聚体的 X 射线结构非常接近 RNase A 的相应二聚体。C 末端的突变影响 N 端α-螺旋的交换能力和两种二聚体形式的稳定性。目前的结果强调了水合壳在确定 RNase A 交换过程中链末端之间的串扰中的重要性。
