D'Ursi A, Oschkinat H, Cieslar C, Picone D, D'Alessio G, Amodeo P, Temussi P A
Dipartimento di Chimica, Università di Napoli Federico II, Italy.
Eur J Biochem. 1995 Apr 15;229(2):494-502. doi: 10.1111/j.1432-1033.1995.tb20490.x.
Monomeric bovine seminal ribonuclease (mBS-RNase), the subunit of dimeric bovine seminal ribonuclease (BS-RNase), is an unusual monomer: for its structural stability, its catalytic activity, which is even higher than that of the parent dimeric enzyme, and for its role as an intermediate in the refolding of dimeric BS-RNase. Here we present the proton NMR assignment and secondary-structure determination of mBS-RNase, with a comparison of its structure to the structure of its parent protein, and to the structure of RNase A, a homologue with more than 80% identity in amino acid sequence. Proton NMR assignment was performed using a computer-assisted procedure, through a partially automated analysis of homonuclear three-dimensional spectra [Oschkinat, H., Holak, T. A. & Cieslar, C. (1991) Biopolymers 31, 699-712]. The secondary structures of mBS-RNase, of the A chain of dimeric BS-RNase, and of RNase A, are found to be similar. Significant differences are found instead, between mBS-RNase and RNase A in the more flexible stretches of the molecule, where a higher number of substitutions is present. Furthermore, a preliminary tertiary-structure model is reported, showing that the overall folding of mBS-RNase is closer to that of RNase A rather than that of (dimeric) BS-RNase.
单体牛精核糖核酸酶（mBS-RNase）是二聚体牛精核糖核酸酶（BS-RNase）的亚基，它是一种不同寻常的单体：就其结构稳定性、甚至高于母体二聚体酶的催化活性以及作为二聚体BS-RNase重折叠中间体的作用而言。在此，我们展示了mBS-RNase的质子核磁共振归属和二级结构测定，并将其结构与其母体蛋白的结构以及核糖核酸酶A（RNase A）的结构进行了比较，RNase A是一种氨基酸序列同一性超过80%的同源物。质子核磁共振归属是通过计算机辅助程序，对同核三维谱进行部分自动化分析来完成的[Oschkinat, H., Holak, T. A. & Cieslar, C. (1991) Biopolymers 31, 699 - 712]。发现mBS-RNase、二聚体BS-RNase的A链以及RNase A的二级结构相似。相反，在分子中更灵活的区域，mBS-RNase和RNase A之间存在显著差异，这些区域存在更多的取代。此外，还报道了一个初步的三级结构模型，表明mBS-RNase的整体折叠更接近RNase A而不是（二聚体）BS-RNase。
