High apparent dielectric constants in the interior of a protein reflect water penetration
High apparent dielectric constants in the interior of a protein reflect water penetration
复制标题
DOI：
10.1016/s0006-3495(00)76411-3
复制
发表时间：
2000-09-01
影响因子：
3.4
通讯作者：
García-Moreno, B
中科院分区：
文献类型：
--
作者：
Dwyer, JJ;Gittis, AG;García-Moreno, B
通过置换瓦尔-66，将谷氨酸埋在葡萄球菌核酸酶的疏水核心中。用平衡热力学方法测定了其pK（a）。它比Glu在水中的pK（a）高4.3个单位。这一增加与先前针对埋在相同位置的赖氨酸测量的4.9单位的Δ pK（a）相当。根据玻恩形式主义，这些Δ pK（a）在能量上等效于带电基团从水转移到介电常数为12的介质。相比之下，干蛋白质粉末的静态介电常数范围为2至4。在V66 E突变体的晶体结构中，可以看到一条水分子链，使埋藏的Glu-66水合并将其与本体溶剂连接。以前从未在超过20种核酸酶结构中检测到掩埋的水分子。的结构和测得的能量构成了令人信服的和前所未有的实验证据，溶剂渗透可以显着地有助于蛋白质内的高表观极化率。为了提高基于结构的计算与连续方法的静电效应，这将是必要的学习，以定量占溶剂渗透的介电效应在蛋白质内部的贡献。
A glutamic acid was buried in the hydrophobic core of staphylococcal nuclease by replacement of Val-66. Its pK(a) was measured with equilibrium thermodynamic methods. it was 4.3 units higher than the pK(a) of Glu in water. This increase was comparable to the Delta pK(a) of 4.9 units measured previously for a lysine buried at the same location. According to the Born formalism these Delta pK(a) are energetically equivalent to the transfer of a charged group from water to a medium of dielectric constant of 12. In contrast, the static dielectric constants of dry protein powders range from 2 to 4. In the crystallographic structure of the V66E mutant, a chain of water molecules was seen that hydrates the buried Glu-66 and links it with bulk solvent. The buried water molecules have never previously been detected in >20 structures of nuclease. The structure and the measured energetics constitute compelling and unprecedented experimental evidence that solvent penetration can contribute significantly to the high apparent polarizability inside proteins. To improve structure-based calculations of electrostatic effects with continuum methods, it will be necessary to learn to account quantitatively for the contributions by solvent penetration to dielectric effects in the protein interior.