Borges Patrícia T, Frazão Carlos, Miranda Cecília S, Carrondo Maria A, Romão Célia V
Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal.
FEBS J. 2014 Sep;281(18):4138-50. doi: 10.1111/febs.12895. Epub 2014 Jul 23.
Deinococcus radiodurans is an aerobic organism with the ability to survive under conditions of high radiation doses or desiccation. As part of its protection system against oxidative stress, this bacterium encodes three monofunctional catalases. The DR1998 catalase belongs to clade 1, and is present at high levels under normal growth conditions. The crystals of DR1998 diffracted very weakly, and the merged diffraction data showed an R sym of 0.308. Its crystal structure was determined and refined to 2.6 Å. The four molecules present in the asymmetric unit form, by crystallographic symmetry, two homotetramers with 222 point-group symmetry. The overall structure of DR1998 is similar to that of other monofunctional catalases, showing higher structural homology with the catalase structures of clade 1. Each monomer shows the typical catalase fold, and contains one heme b in the active site. The heme is coordinated by the proximal ligand Tyr369, and on the heme distal side the essential His81 and Asn159 are hydrogen-bonded to a water molecule. A 25-Å-long channel is the main channel connecting the active site to the external surface. This channel starts with a hydrophobic region from the catalytic heme site, which is followed by a hydrophilic region that begins on Asp139 and expands up to the protein surface. Apart from this channel, an alternative channel, also near the heme active site, is presented and discussed.
Coordinates and structure factors have been deposited in the Protein Data Bank in Europe under accession code 4CAB.
耐辐射球菌是一种需氧生物，能够在高辐射剂量或干燥条件下存活。作为其抗氧化应激保护系统的一部分，这种细菌编码三种单功能过氧化氢酶。DR1998过氧化氢酶属于第1进化枝，在正常生长条件下含量很高。DR1998的晶体衍射非常弱，合并后的衍射数据显示R sym为0.308。确定了其晶体结构并将其精修至2.6 Å。不对称单元中存在的四个分子通过晶体学对称性形成两个具有222点群对称性的同四聚体。DR1998的整体结构与其他单功能过氧化氢酶相似，与第1进化枝的过氧化氢酶结构具有更高的结构同源性。每个单体都呈现出典型的过氧化氢酶折叠结构，在活性位点含有一个血红素b。血红素由近端配体Tyr369配位，在血红素远端，必需的His81和Asn159与一个水分子形成氢键。一条25 Å长的通道是连接活性位点与外表面的主要通道。这条通道从催化血红素位点的疏水区域开始，接着是一个亲水区域，该区域从Asp139开始并延伸至蛋白质表面。除了这条通道外，还展示并讨论了另一条也靠近血红素活性位点的通道。
坐标和结构因子已存入欧洲蛋白质数据银行，登录代码为4CAB。
