CRYSTALLOGRAPHIC ANALYSES OF SITE-DIRECTED MUTANTS OF THE PHOTOSYNTHETIC REACTION-CENTER FROM RHODOBACTER-SPHAEROIDES
CRYSTALLOGRAPHIC ANALYSES OF SITE-DIRECTED MUTANTS OF THE PHOTOSYNTHETIC REACTION-CENTER FROM RHODOBACTER-SPHAEROIDES
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DOI：
10.1021/bi00181a020
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发表时间：
1994-04-19
期刊：
影响因子：
2.9
通讯作者：
REES, DC
中科院分区：
文献类型：
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作者：
CHIRINO, AJ;LOUS, EJ;REES, DC
从球形红细菌的2.4.1和WS 231野生型菌株中获得了7个细菌光合反应中心（RC）的定点突变体，并对其进行了结晶和X射线衍射分析，其分辨率在3.0和4.0埃之间。这些突变可分为四类：（1）改变辅因子组成的突变，影响电子传递和量子产率，His M202 → Leu（M202 HL），His L173 → Leu（L173 HL），Leu M214 → His（M214 LH）;（2）电子转移途径中的突变改变了电子转移动力学，Tyr M210 → Phe（M210 YF）;（3）在非血红素铁附近的突变导致无铁反应中心，His M219 -> Cys（M219 HC）;和（4）次级电子受体（泛醌）周围的突变，影响质子转移和醌周转，Glu L212 -> Gln（L212EQ）和Asp L213 -> Asn（L213DN）。残基L173和M202在BChl特殊对的两个细菌叶绿素的相应镁的键合距离内，而M214靠近RC的活性A分支上的细菌脱镁叶绿素。L173 HL和M202 HL晶体结构表明，各自的细菌叶绿素被细菌脱镁叶绿素取代（即，镁的损失），而对周围的主链或侧链原子没有显著的结构扰动。在M214 LH突变体中，细菌叶绿素已被细菌叶绿素取代，并且His M214的侧链在镁的配体距离内。M210 YF、L212 EQ和L213 DN突变体在突变位点附近没有显示出显著的三级结构变化。M219 HC衍射数据表明，在不存在非血红素铁的情况下，反应中心的整体三级结构得以保持。
Seven site-directed mutants of the bacterial photosynthetic reaction center (RC) from the 2.4.1 and WS 231 wild-type strains of Rhodobacter sphaeroides have been crystallized and their X-ray diffraction analyzed to resolutions between 3.0 and 4.0 Angstrom. The mutations can be divided into four distinct categories: (1) mutations altering cofactor composition that affect electron transfer and quantum yield, His M202 --> Leu (M202HL), His L173 --> Leu (L173HL), and Leu M214 --> His (M214LH); (2) a mutation in the proposed pathway of electron transfer altering electron-transfer kinetics, Tyr M210 --> Phe (M210YF); (3) a mutation around the non-heme iron resulting in an iron-less reaction center, His M219 --> Cys (M219HC); and (4) mutations around the secondary electron acceptor, a ubiquinone, affecting proton transfer and quinone turnover, Glu L212 --> Gin (L212EQ) and Asp L213 --> Asn (L213DN). Residues L173 and M202 are within bonding distance of the respective magnesiums of the two bacteriochlorophylls of the BChl special pair, while M214 is close to the bacteriopheophytin on the active A branch of the RC. The L173HL and M202HL crystal structures show that the respective bacteriochlorophylls are replaced with bacteriopheophytins (i.e., loss of magnesium) without significant structural perturbations to the surrounding main-chain or side-chain atoms. In the M214LH mutant, the bacteriopheophytin has been replaced by a bacteriochlorophyll, and the side chain of His M214 is within ligand distance of the magnesium. The M210YF, L212EQ, and L213DN mutants show no significant tertiary structure changes near the mutation sites. The M219HC diffraction data indicate that the overall tertiary structure of the reaction center is maintained in the absence of the non-heme iron.