The structure of mouse testicular lactate dehydrogenase isoenzyme C4 at 2.9 A resolution.
The structure of mouse testicular lactate dehydrogenase isoenzyme C4 at 2.9 A resolution.
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小鼠睾丸乳酸脱氢酶同工酶 C4 的结构，分辨率为 2.9 A。
DOI：
10.2210/pdb1ldx/pdb
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发表时间：
1978
期刊：
影响因子：
--
通讯作者：
M. Rossmann
中科院分区：
文献类型：
--
作者：
W. D. Musick;M. Rossmann
采用分子置换技术，以2.9A的分辨率解析了小鼠睾丸乳酸脱氢酶同工酶C_4的结构。电子密度图揭示了一个三进制样的配置的灵活的环肽，虽然密度对应的辅酶和底物分子不存在。显然，溶液中的脱辅基乳酸脱氢酶分子处于O（如在角鲨脱辅基乳酸脱氢酶M4中发现的开环）和C（如在各种三元复合物中发现的闭环）构象之间的动态平衡。在脱辅基酶的结晶过程中，选择一种或另一种构象异构体。脱辅基乳酸脱氢酶C4分子的闭合构象的表观稳定性可以部分解释C同工酶的低催化周转数。在位置30处的精氨酸残基的可能取代也可能是促成因素，以及允许NADP充当辅酶。
The structure of lactate dehydrogenase isoenzyme C4 from mouse testes was solved at 2.9 A resolution using the technique of molecular replacement. The electron density map revealed a ternary-like configuration of the flexible loop peptide although density corresponding to the coenzyme and substrate molecules was not present. Apparently the apo-lactate dehydrogenase molecule in solution is in a dynamic equilibrium between the O (loop open as found in dogfish apo-lactate dehydrogenase M4) and C (loop closed as found in a variety of ternary complexes) conformations. During crystallization of the apoenzyme one or the other conformers is selected. The apparent stability of the closed conformation for the apo-lactate dehydrogenase C4 molecule may in part explain the low catalytic turnover number of the C isoenzyme. A possible substitution of an arginine residue at position 30 may also be a contributing factor as well as allowing NADP to act as coenzyme.