Pace C N, Grimsley G R
Biochemistry Department, Texas A&M University, College Station 77843.
Biochemistry. 1988 May 3;27(9):3242-6. doi: 10.1021/bi00409a018.
The stability of the folded conformation of ribonuclease T1 is increased by 0.8, 1.8, and 3.3 kcal/mol in the presence of 0.1 M NaCl, MgCl2, and Na2HPO4, respectively. This remarkable increase in the conformational stability results primarily from the preferential binding to the native protein of one Mg2+ or two Na+ ions at cation-binding sites and by the binding of one HPO4(2-) ion at an anion-binding site. Only modest binding constants, 6.2 (Na+), 155 (Mg2+), and 282 M-1 (HPO4(2-)), are required to account for the enhanced stability. One important goal of the modification of proteins through genetic engineering is to increase their stability. Our results suggest that the creation of specific cation- and anion-binding sites on the surface of a protein through amino acid substitutions might be a generally useful way of achieving this goal. The design of these sites will be aided by the recent availability of detailed structural information on cation- and anion-binding sites.
在分别存在0.1 M NaCl、MgCl₂和Na₂HPO₄的情况下，核糖核酸酶T1折叠构象的稳定性分别提高了0.8、1.8和3.3千卡/摩尔。这种构象稳定性的显著提高主要源于阳离子结合位点上一个Mg²⁺或两个Na⁺离子与天然蛋白质的优先结合，以及阴离子结合位点上一个HPO₄²⁻离子的结合。仅需适度的结合常数，即6.2（Na⁺）、155（Mg²⁺）和282 M⁻¹（HPO₄²⁻），就能解释稳定性的增强。通过基因工程对蛋白质进行修饰的一个重要目标是提高其稳定性。我们的结果表明，通过氨基酸替换在蛋白质表面创建特定的阳离子和阴离子结合位点可能是实现这一目标的一种普遍有用的方法。这些位点的设计将得益于最近关于阳离子和阴离子结合位点的详细结构信息的可得性。
