An arginine to lysine mutation in the vicinity of the heme propionates affects the redox potentials of the hemes and associated electron and proton transfer in cytochrome c oxidase.
An arginine to lysine mutation in the vicinity of the heme propionates affects the redox potentials of the hemes and associated electron and proton transfer in cytochrome c oxidase.
复制标题
丙酸血红素附近的精氨酸到赖氨酸的突变影响血红素的氧化还原电位以及细胞色素c氧化酶中相关的电子和质子转移。
DOI：
10.1021/bi050283d
复制
发表时间：
2005
期刊：
影响因子：
2.9
通讯作者：
Ferguson-Miller,Shelagh
中科院分区：
文献类型：
--
作者：
Mills,DeniseA;Geren,Lois;Hiser,Carrie;Schmidt,Bryan;Durham,Bill;Millett,Francis;Ferguson-Miller,Shelagh
Cytochromecoxidase pumps protons across a membrane using energy from electron transfer and reduction of oxygen to water. It is postulated that an element of the energy transduction mechanism is the movement of protons to the vicinity of the hemes upon reduction, to favor charge neutrality. Possible sites on which protons could reside, in addition to the conserved carboxylate E286, are the propionate groups of hemeaand/or hemea3. A highly conserved pair of arginines (R481 and R482) interact with these propionates through ionic and hydrogen bonds. This study shows that the conservative mutant, R481K, although as fully active as the wild type under many conditions, exhibits a significant decrease in the midpoint redox potential of hemearelative to CuA(ΔEm) of ≅40 mV, has lowered activity under conditions of high pH or in the presence of a membrane potential, and has a slowed hemea3reduction with dithionite. Another mutant, D132A, which strongly inhibits proton uptake from the internal side of the membrane, has <4% of the activity of the wild type and appears to be dependent on proton uptake from the outside. A double mutation, D132A/R481K, is even more strongly inhibited (∼1% of that of the wild type). The more-than-additive effect supports the concept that R481K not only lowers the midpoint potential of hemeabut also limits a supply route for protons from the outside of the membrane used by the D132 mutant. The results are consistent with an important role of R481 and hemea/a3propionates in proton movement in a reversible exit path.
