几种重要蛋白质的结构与功能研究

This project include three aspects: (1) elucidation the structural mechanism and functional importance of a non-prolin cis peptide found in the neurotoxin from scorpion Buthus martensii Karsch (BmK): (2) determination the crystal structure of human growth factor (EGF) based on which to understand the structural basis for EGF-receptor binding; (3) expression, purification and crystallization of the cell signal transduction protein JUNK2 and P38..It is almost a dogma that the peptide bond in protein always takes trans configuration because it is energetically more favorable than the cis form. The crystal structures of three a-like toxins, two monomers and a dimmer, from BmK venom with different potency, distinct crystal form have been determined at high resolution. They all show a non-prolin cis peptide occurred between residues 9 and 10. Detailed analysis suggested the main structural elements and possible functional roles for cis form. On basis of these about 20 relevant mutants were constructed, expressed with a yeast system, and tested by using a bioassay in mice and electrophysiological characterization on cloned Na+ channel. The result identified a functional site (the site RC) in which the cis peptide bond mediated the unique tertiary structures. Besides, the X-ray structures for a series of mutants were elucidated, which interestingly revealed that the substitution of residue 8 Lys by Asp will induce the change from the cis form to trans form. Therefore the reside 8 Lys/Asp seems to be a "switch" for the cis/trans isomorization. These results manifested a way to achieve high levels of molecular specificity and atomic precision through the strained backbone geometry..Epidermal growth factor (EGF) is a typical growth-stimulating peptide and functions by binding to specific cell-surface receptors and inducing dimerization of the receptors. Little is known about the molecular mechanism of EGF-induced dimerization of EGF receptors. The crystal structure of human EGF has been determined at pH 8.1. There are two human EGF molecules A and B in the asymmetric unit of the crystals, which form a potential dimmer. Importantly, a number of residues known to be indispensable for EGF binding to its receptor are involved in the interface between the two EGF molecules, suggesting a crucial role of EGF dimerization in the EGF-induced dimerization of receptors. In addition, the crystal structure of EGF shares the main features of the NMR structure of mouse EGF determined at pH 2.0, but structural comparisons between different models have revealed new detailed features and properties of the EGF structure...

从中国马氏钳蝎（BmK）神经毒素中发现含有反常顺式肽键的新类型，这在国际上尚属首例１狙芯磕馔ü徊讲舛钢諦mK分子的溶液结构和晶体结构，查明cis肽在BmK中出现的普遍性；同时通过基因定位诱变研究该cis肽产生的立体化学原因和对应的蛋白质序列特征；沂靖美嗌窬舅氐恼褰峁固卣鳎谛窬舅刂械姆掷喽ㄎ唬捌涠捞氐墓δ芤庖濉