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首页> 外文期刊>Biochemistry >INTERACTION OF AN ENGINEERED [3FE-4S] CLUSTER WITH A MENAQUINOL BINDING SITE OF ESCHERICHIA COLI DMSO REDUCTASE
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INTERACTION OF AN ENGINEERED [3FE-4S] CLUSTER WITH A MENAQUINOL BINDING SITE OF ESCHERICHIA COLI DMSO REDUCTASE

机译：工程化的[3FE-4S]簇与大肠埃希氏菌DMSO还原酶的甲基萘酚结合位点的相互作用

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摘要

We have characterized by EPR the interaction of the E(m,7) = -50 mV [4Fe-4S] cluster of Escherichia coli DMSO reductase (DmsABC) with a menaquinol (MQH(2)) binding site. Potentiometric titrations indicate that in DmsAB(C102S)C, the E(m,7) = -50 mV [4Fe-4S] cluster is replaced by an E(m,7) = +260 mV [3Fe-4S] cluster. The Q-pool coupling assay in combination with the MQH(2) analog HOQNO (2-n-heptyl-4-hydroxyquinoline-N-oxide) was used to examine the effect of the DmsB(C102S) mutation on physiological electron transfer through DmsABC. Forward electron transfer through the mutant (MQH(2) to DmsA) is blocked in the Q-pool coupling assay, but reverse electron transfer (DmsA to MQ) is not. HOQNO elicits a significant change in the EPR line Shape of the oxidized DmsAB(C102S)C [3Fe-4S] cluster but has no effect on the line shape of the reduced [4Fe-4S] clusters. We have identified a residue in DmsC involved in MQH(2) oxidation, DmsC(H65), and in a double mutant, DmsAB(C102S)C(H65R), the DmsC mutation blocks the HOQNO effect on the [3Fe-4S] EPR line shape, suggesting that the DmsC(H65R) mutation either blocks HOQNO binding or blocks a conformational link between a HOQNO binding site and the DmsB(C102S) [3Fe-4S] cluster. These results suggest that the MQH(2) binding site of DmsC is conformationally and functionally linked to the E(m,7) = -50 mV [4Fe-4S] cluster of DmsB.
机译：我们已经通过EPR表征了大肠杆菌DMSO还原酶（DmsABC）与甲萘醌（MQH（2））结合位点的E（m，7）= -50 mV [4Fe-4S]簇的相互作用。电位滴定表明，在DmsAB（C102S）C中，E（m，7）= -50 mV [4Fe-4S]簇被E（m，7）= +260 mV [3Fe-4S]簇代替。 Q池耦合测定结合MQH（2）类似物HOQNO（2-n-庚基-4-羟基喹啉-N-氧化物）用于检查DmsB（C102S）突变对通过DmsABC进行的生理电子转移的影响。通过突变体（MQH（2）到DmsA）的正向电子转移在Q池偶联测定中被阻止，但是反向电子转移（从DmsA到MQ）则没有。 HOQNO引起了氧化的DmsAB（C102S）C [3Fe-4S]簇的EPR线形的显着变化，但对还原的[4Fe-4S]簇的线形没有影响。我们已经确定了参与MQH（2）氧化的DmsC中的残基DmsC（H65），以及在双突变体DmsAB（C102S）C（H65R）中的残基，DmsC突变阻止了HOQNO对[3Fe-4S] EPR的影响线形，表明DmsC（H65R）突变要么阻断HOQNO结合，要么阻断HOQNO结合位点与DmsB（C102S）[3Fe-4S]簇之间的构象连接。这些结果表明，DmsC的MQH（2）结合位点在构象和功能上与DmsB的E（m，7）= -50 mV [4Fe-4S]簇相连接。

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