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首页> 外文期刊>Biochemistry >Role of a Highly Conserved Electrostatic Interaction on the Surface of Cytochrome c in Control of the Redox Function
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Role of a Highly Conserved Electrostatic Interaction on the Surface of Cytochrome c in Control of the Redox Function

机译：细胞色素c表面上高度保守的静电相互作用在氧化还原功能控制中的作用

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In Hydrogenobacter thermophilus cytochrome c552, an electrostatic interaction between Lys8 andnGlu68 in the N- and C-terminal helices, respectively, stabilizes its protein structure [Travaglini-Allocatelli,nC., Gianni, S., Dubey, V. K., Borgia, A., Di Matteo, A., Bonivento, D., Cutruzzola, F., Bren, K. L., andnBrunori, M. (2005) J. Biol. Chem. 280, 25729-25734], this electrostatic interaction being a highly conservednstructural feature of the cytochrome c family. In the present study, the functional consequences of removal ofnthe interaction through replacement of Lys8 by Ala have been investigated in order to elucidate themolecularnmechanisms responsible for functional control of the protein. The mutation resulted in a decrease in proteinnstability, as reflected in lowering of the denaturation temperature by ∼2-9 u0001C, and a negative shift by ∼8mVnof the redox potential (Em) of the protein. The decrease in the protein stability was attributed to the enthalpicnloss due to the removal of the intramolecular interaction. The negative shift of the Em value was shown to bendue to the effect of the mutation on the entropic contribution to the Em value. The small, but subtle, effects ofnremoval of the conserved electrostatic interaction, occurring at ∼1.4 nm away from heme iron, on thenthermodynamic properties of the protein demonstrated not only that the interaction is important fornmaintaining the functional properties of the protein but also that amino acid residues relatively remote fromnthe heme active site play sizable roles in functional control of the protein.
机译：在嗜热氢杆菌细胞色素c552中，Ls8和nGlu68之间N和C末端螺旋之间的静电相互作用分别稳定了其蛋白质结构[Travaglini-Allocatelli，nC。，Gianni，S.，Dubey，VK，Borgia，A.， Di Matteo，A.，Bonivento，D.，Cutruzzola，F.，Bren，KL，andnBrunori，M.（2005）J.化学280，25729-25734]，这种静电相互作用是细胞色素c家族的高度保守的结构特征。在本研究中，为了阐明负责蛋白质功能控制的分子机制，已经研究了通过用Ala取代Lys8去除相互作用的功能后果。突变导致蛋白质稳定性降低，这反映在变性温度降低约2-9 u0001C的同时，蛋白质的氧化还原电位（Em）降低了约8mVn。蛋白质稳定性的下降归因于分子内相互作用的去除而引起的焓焓损失。 Em值的负向偏移显示出突变对熵对Em值的影响。距血红素铁约1.4 nm处的保守静电相互作用的微小但微妙的消除对蛋白质的热力学性质的影响不仅表明该相互作用对于维持蛋白质的功能性质很重要，而且氨基酸相对于血红素活性位点相对较远的残基在蛋白质的功能控制中起相当大的作用。

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