Structure of a novel dodecaheme cytochrome c from Geobacter sulfurreducens reveals an extended 12 nm protein with interacting hemes
Structure of a novel dodecaheme cytochrome c from Geobacter sulfurreducens reveals an extended 12 nm protein with interacting hemes
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DOI：
10.1016/j.jsb.2010.11.022
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发表时间：
2011-04-01
影响因子：
3
通讯作者：
Schiffer, M.
中科院分区：
文献类型：
--
作者：
Pokkuluri, P. R.;Londer, Y. Y.;Schiffer, M.
多血红素细胞色素c是重要的电子转移途径，在减少可溶性和不溶性的铁（III）的Geophylsulfurreducens。我们确定了第一个十二血红素细胞色素c（GSU 1996）沿着在3.2埃分辨率的晶体结构，其N-末端和C-末端六血红素片段分别在2.6和2.15埃分辨率。测定了全长蛋白质及其片段的宏观还原电位。GSU 1996的序列可分为四个c（7）型结构域（A、B、C和D），与三血红素细胞色素c（7）具有同源性。在细胞色素c（7）中，所有三个血红素都是双组氨酸配位的，而在c（7）型结构域中，最后一个血红素是组氨酸-蛋氨酸配位的。全长GSU 1996具有12 nm长的新月形结构，其中12个血红素沿着多肽排列以形成血红素的“纳米线”;它具有模块化结构。令人惊讶的是，虽然蛋白质的C-末端一半由两个单独的c（7）-型结构域（C和D）组成，通过小接头连接，但蛋白质的N-末端一半具有形成一个结构单元的两个c（7）-型结构域（A和B）。在AB片段中也观察到这一点。在结构域A和B的界面处的血红素之间存在意想不到的相互作用，其形成具有其卟啉环的几乎平行堆叠的血红素对。在整个蛋白质中彼此相邻的血红素在货车德瓦尔斯距离内，这使得它们之间能够进行有效的电子交换。第一次，从一个多血红素蛋白的c（7）型结构域的结构细节进行了比较。(C)2010年爱思唯尔公司All rights reserved.
Multiheme cytochromes c are important in electron transfer pathways in reduction of both soluble and insoluble Fe(III) by Geobacter sulfurreducens. We determined the crystal structure at 3.2 angstrom resolution of the first dodecaheme cytochrome c (GSU1996) along with its N-terminal and C-terminal hexaheme fragments at 2.6 and 2.15 angstrom resolution, respectively. The macroscopic reduction potentials of the full-length protein and its fragments were measured. The sequence of GSU1996 can be divided into four c(7)-type domains (A, B, C and D) with homology to triheme cytochromes c(7). In cytochromes c(7) all three hemes are bis-His coordinated, whereas in c(7)-type domains the last heme is His-Met coordinated. The full-length GSU1996 has a 12 nm long crescent shaped structure with the 12 hemes arranged along a polypeptide to form a "nanowire" of hemes; it has a modular structure. Surprisingly, while the C-terminal half of the protein consists of two separate c(7)-type domains (C and D) connected by a small linker, the N-terminal half of the protein has two c(7)-type domains (A and B) that form one structural unit. This is also observed in the AB fragment. There is an unexpected interaction between the hemes at the interface of domains A and B, which form a heme-pair with nearly parallel stacking of their porphyrin rings. The hemes adjacent to each other throughout the protein are within van der Waals distance which enables efficient electron exchange between them. For the first time, the structural details of c(7)-type domains from one multiheme protein were compared. (C) 2010 Elsevier Inc. All rights reserved.