Identification and characterization of solvent-filled channels in human ferrochelatase.
Identification and characterization of solvent-filled channels in human ferrochelatase.
复制标题
人亚铁螯合酶中溶剂填充通道的鉴定和表征。
DOI：
10.1021/bi300598g
复制
发表时间：
2012
期刊：
影响因子：
2.9
通讯作者：
Dailey,HarryA
中科院分区：
文献类型：
--
作者：
Medlock,AmyE;Najahi-Missaoui,Wided;Ross,TeresaA;Dailey,TamaraA;Burch,Joseph;O'Brien,JessicaR;Lanzilotta,WilliamN;Dailey,HarryA
铁螯合酶催化两种潜在细胞毒性产物铁和原卟啉 IX 形成原血红素。虽然从人亚铁螯合酶的结构和动力学研究中了解到该酶在催化过程中的动态性质以及原卟啉 IX 和血红素的结合，但对于金属如何传递到活性位点以及螯合如何发生却知之甚少。对迄今为止所有可用的亚铁螯合酶结构的分析揭示了几个充满溶剂的通道的存在，这些通道起源于蛋白质表面并延续到活性位点。这些通道已被提议为催化循环期间的底物进入、水进入和质子退出提供路线。为了开始了解这些通道的功能，我们在体外和体内研究了这些充满溶剂的通道的许多变体。本文提供的数据支持这些通道之一（源自表面残基 H240）在将铁递送至活性位点中的作用。对位于活性位点袋背面的保守残基 F337 的精氨酰变体的结构研究表明，它不仅调节活性位点通道的打开和关闭，而且在调节酶机制中发挥作用。这些数据提供了对底物和水进出活性位点的运动以及这种运动如何与反应机制协调的深入了解。
Ferrochelatase catalyzes the formation of protoheme from two potentially cytotoxic products, iron and protoporphyrin IX. While much is known from structural and kinetic studies on human ferrochelatase of the dynamic nature of the enzyme during catalysis and the binding of protoporphyrin IX and heme, little is known about how metal is delivered to the active site and how chelation occurs. Analysis of all ferrochelatase structures available to date reveals the existence of several solvent-filled channels that originate at the protein surface and continue to the active site. These channels have been proposed to provide a route for substrate entry, water entry, and proton exit during the catalytic cycle. To begin to understand the functions of these channels, we investigated in vitro and in vivo a number of variants that line these solvent-filled channels. Data presented herein support the role of one of these channels, which originates at the surface residue H240, in the delivery of iron to the active site. Structural studies of the arginyl variant of the conserved residue F337, which resides at the back of the active site pocket, suggest that it not only regulates the opening and closing of active site channels but also plays a role in regulating the enzyme mechanism. These data provide insight into the movement of the substrate and water into and out of the active site and how this movement is coordinated with the reaction mechanism.