Kéry V, Both V, Sevcík J, Zelinka J
Gen Physiol Biophys. 1986 Aug;5(4):405-14.
The number and role of histidine residues in the active site of extracellular guanyloribonuclease Sa produced by Streptomyces aureofaciens (RNAase Sa) were studied via chemical modification by ethoxyformic anhydride by means of circular dichroism measurements. It was shown that only one of two histidines of RNAase Sa is situated in the active site of the enzyme. Ethoxyformylation of RNAase Sa in the presence of Guo-3'-P, Guo-5'-P and dGuo-5-P, all of them being competitive inhibitors of the enzyme, supported the assumption that an essential histidine residue is bound to the phosphate group in the position 3' of the ribose ring. The circular dichroism measurements of native and modified RNAase Sa and of its complex with Guo-3'-P showed that the modification of the essential histidine residue resulted in alteration of binding of RNAase Sa to Guo-3'-P; histidine thus may play a key role in the formation of such a complex.
通过利用圆二色性测量法，借助乙氧基甲酸酐进行化学修饰，研究了金色链霉菌产生的细胞外鸟苷酸核糖核酸酶Sa（RNA酶Sa）活性位点中组氨酸残基的数量和作用。结果表明，RNA酶Sa的两个组氨酸中只有一个位于酶的活性位点。在鸟苷-3'-磷酸（Guo-3'-P）、鸟苷-5'-磷酸（Guo-5'-P）和脱氧鸟苷-5'-磷酸（dGuo-5-P）存在的情况下对RNA酶Sa进行乙氧基甲酰化，这三种物质均为该酶的竞争性抑制剂，这支持了一个基本的组氨酸残基与核糖环3'位的磷酸基团结合的假设。对天然和修饰后的RNA酶Sa及其与Guo-3'-P复合物的圆二色性测量表明，基本组氨酸残基的修饰导致RNA酶Sa与Guo-3'-P结合的改变；因此，组氨酸可能在这种复合物的形成中起关键作用。
