CIRCULAR DICHROISM AND UV IRRADIATION INDUCED STRUCTURAL CHANGES OF A TOBAMOVIRUS

Over the range of pH 5—10.8, CCGCV showed the same spectrum which was affected only slightly by the variation in the salt concentration. The CD of the free coat protein and free RNA of this virus has also been measured, Results showed that the contribution of the protein component to the far UV CD spectrum of CCGCV was dominant. The near UV CD spectrum may be indicative of a strong intravirus interaction of the RNA with the coat protein.When irradiated with 234 or 221 nm light, CCGCV in saline over the range of pit 3.1—4.8 showed an unusual change in the ellipticities at the corresponding wavelengths. The CD spectrum of CCGCV after irradiation showed two strong positive peaks at 230—231nm and around 205 nm. The mechanism of producing this phenomenon is discussed.     

一个烟草花叶病毒株的圆二色性和紫外照射诱发的结构变化

本文证明在pH 5—10.8的范围里,CCGCV的生理盐水溶液呈相同的CD谱。溶液中不同盐浓度对此病毒的CD谱没有明显影响。也测定了此病毒的游离外壳蛋白质和游离核酸的CD谱。实验结果说明CCGCV的远紫外CD谱几乎完全由蛋白质组份贡献。近紫外CD谱可能说明病毒颗粒内RNA和蛋白质问有很强的相互作用。在234或221毫微米光照下,pH 3.1—4.8时的CCGCV生理盐水溶液在相应波长处的椭圆值呈现一种不寻常的变化。光照后的病毒的CD谱在231—230毫微米和205毫微米附近各呈现一个强正峰。讨论了产生此种现象的机制。     

绿豆胰蛋白酶抑制剂的研究——Lys活性碎片的还原及重氧化

本文证明绿豆胰蛋白酶抑制剂Lys活性碎片由 A_1,A_2两条肽链通过两对二硫键联结而成,今通过DTT还原及凝胶过滤可将A_1(26个氨基酸残基),A_2(9个氨基酸残基)两肽链拆分.还原型的A_1肽链重氧化后活力的回收率是原有活性碎片总活力的25%.经固相胰蛋白酶亲和层析纯化的A_1活性碎片以单体和二聚体两种分子形式存在,两者可在Sephadex G-25柱上分开,以单体为主,二聚体活性较低.此结果进一步证实,绿豆胰蛋白酶抑制剂的分子进化过程是由一原始单头抑制剂通过基因重复及基因突变演化而来。此外比较了Lys活性碎片和重氧化肽链A_1的CD图谱。     

STUDIES ON THE MUNG BEAN TRYPSIN INHIBITOR——REDUCTION AND REOXIDATION OF THE DISULFIDE BONDS OF THE LYS ACTIVE FRAGMENT

Two peptide chains A_1 and A_2 of the Lys active fragment, linked via a couple ofinter-disulfide bonds, could be separated from each other after reduction with dithiothreitoland gel filtration on Sephadex G-25. Reoxidation of the reduced peptide chain A_1 resultedin recovering the inhibitory activity with 25% yield, based on the original activity of theLys fragment. The A_1 active fragment was further purified by affinity chromatographywith immobilized trypsin. Sephadex G-25 gel filtration produced two forms of the A_1 activefragment, the major fraction being a monomer and the minor one being a dimeer with loweractivity. The results obtained offered evidence of the evolution of mung bean inhibitorfrom an ancestral single-headed inhibitor by fused gene duplication with A_2 as a connectingpeptide. The CD spectra of the Lys fragment and the reoxidized peptide chain A_1 werealso compared.