STRUCTURE OF THE ACTIVE TERNARY COMPLEX OF PIG-HEART LACTATE-DEHYDROGENASE WITH S-LAC-NAD AT 2.7 A RESOLUTION
STRUCTURE OF THE ACTIVE TERNARY COMPLEX OF PIG-HEART LACTATE-DEHYDROGENASE WITH S-LAC-NAD AT 2.7 A RESOLUTION
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DOI：
10.1016/0022-2836(81)90516-7
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发表时间：
1981-01-01
影响因子：
5.6
通讯作者：
ROSSMANN, MG
中科院分区：
文献类型：
--
作者：
GRAU, UM;TROMMER, WE;ROSSMANN, MG
以活性辅酶底物类似物（3S）-5-（3-羧基-3-羟丙基）NAD+为配体，对猪心乳酸脱氢酶（LDH）的结构进行了高分辨解析。底物和活性位点的安排密切类似于早期提出的活性三元复合物的LDH和显着不同，在流产的三元复合物的角鲨M4 [肌肉] LDH。小的差异，相对于三元抑制剂复合物的角鲨M4 LDH发生在辅酶的构象，以及在辅酶结合位点的蛋白质侧链的空间排列。该环是在一个整体封闭的构象典型的LDH三元复合物，虽然它略有不同，从角鲨M4 LDH三元复合物中发现的构象。NAD与心脏同工酶的更强结合不能通过经由谷氨酰胺31与焦磷酸基团的额外H-键来解释。角鲨M4乳酸脱氢酶中P轴相关亚基之间的阴离子结合位点也存在于猪H4 LDH中。认为LDH催化内部酸/碱催化剂His 195的pK值受到环残基Arg 109的调节，导致底物活化。
The structure of pig heart lactate dehydrogenase [LDH] complexed with the active coenzyme substrate analog (3S)-5-(3-carboxy-3-hydroxypropyl) NAD+ was solved to high resolution. The substrate and active site arrangements resemble closely the earlier proposed active ternary complex of LDH and differ significantly from those in abortive ternary complexes of dogfish M4 [muscle] LDH. Small differences with respect to ternary inhibitor complexes of dogfish M4 LDH occur in the coenzyme conformation as well as in the spatial arrangement of protein side-chains at the coenzyme binding site. The loop is in an overall closed conformation typical for ternary complexes of LDH, although it differs slightly from the conformation found in dogfish M4 LDH ternary complexes. The stronger binding of NAD to the heart isoenzyme cannot be accounted for by an additional H-bond to the pyrophosphate group via glutamine 31. The anion binding sites found between P axis-related subunits in dogfish M4 lactate dehydrogenase are also present in pig H4 LDH. It is proposed that LDH catalysis the pK value of the internal acid/base catalyst His195 is modulated by loop residue Arg109, leading to substrate activation.