Davis A, Moore I B, Parker D S, Taniuchi H
J Biol Chem. 1977 Sep 25;252(18):6544-53.
During purification of nuclease (redisignated as nuclease A in the present studies) from the culture media of Staphylococcus aureus strain Foggi, three enzymacally active second species (nucleases B1, B2, and B3) were isolated as a mixture by ion exchange chromatography. Examination of the amino acid sequence of these second species indicates that nucleases B1, B2, and B3 apparently contain the same sequence as that of nuclease A with an extra sequence Ser-Gln-Thr-Asp-Asx-Gly-Val-Asx-Arg-Ser-Gly-Ser-Glu-Asp-Pro-Thr-Val-Tyr-Ser linked through a peptide bond to the NH2 terminus of the nuclease A portion. In nuclease B1 the 2 residues indicated by Asx are aspartic acid, in nuclease B2 the first and the second Asx from the NH2 terminus are aspartic acid and asparagine, respectively, and in nuclease B3 both Asx are asparagine. These second species do not contain a significant amount of carbohydrate. The extra amino acid sequence appears to be flexible and does not interfere with the ordered structure and function of the nuclease A portion. The nuclease A portion was recovered, in part, from a mixture of these nuclease B species after digestion with staphylococcal protease in the presence of ligands, deoxythymidine 3',5'-diphosphate, and calcium ion. Thus, these nuclease B species may be closely related to, if not identical with, a precursor of nuclease A. Similar second species of nuclease have been found in strain V8.
在从金黄色葡萄球菌福吉菌株的培养基中纯化核酸酶（在本研究中重新命名为核酸酶A）的过程中，通过离子交换色谱法分离出三种具有酶活性的第二种物质（核酸酶B1、B2和B3）的混合物。对这些第二种物质的氨基酸序列进行检查表明，核酸酶B1、B2和B3显然包含与核酸酶A相同的序列，其额外序列Ser-Gln-Thr-Asp-Asx-Gly-Val-Asx-Arg-Ser-Gly-Ser-Glu-Asp-Pro-Thr-Val-Tyr-Ser通过肽键连接到核酸酶A部分的NH2末端。在核酸酶B1中，由Asx表示的2个残基是天冬氨酸，在核酸酶B2中，从NH2末端起的第一个和第二个Asx分别是天冬氨酸和天冬酰胺，在核酸酶B3中，两个Asx都是天冬酰胺。这些第二种物质不含大量碳水化合物。额外的氨基酸序列似乎具有灵活性，并且不干扰核酸酶A部分的有序结构和功能。在配体、脱氧胸苷3',5'-二磷酸和钙离子存在下用葡萄球菌蛋白酶消化后，从这些核酸酶B物质的混合物中部分回收了核酸酶A部分。因此，这些核酸酶B物质即使与核酸酶A的前体不完全相同，也可能与之密切相关。在V8菌株中也发现了类似的核酸酶第二种物质。
