Identification of amino acid residues in a proton release pathway near the bacteriochlorophyll dimer in reaction centers from Rhodobacter sphaeroides
Identification of amino acid residues in a proton release pathway near the bacteriochlorophyll dimer in reaction centers from Rhodobacter sphaeroides
复制标题
DOI：
10.1007/s11120-022-00968-x
复制
发表时间：
2022-10-05
影响因子：
3.7
通讯作者：
Williams, J. C.
中科院分区：
文献类型：
--
作者：
Allen, J. P.;Chamberlain, K. D.;Williams, J. C.
质子转移的控制，细胞功能的一个重要属性，可以从细菌反应中心的调查获得洞察。虽然与醌的还原相关的质子的吸收被很好地表征，但与氧化的细菌叶绿素二聚体相关的质子的释放却知之甚少。光谱和质子释放/吸收测量被用来检查质子释放特性的12个突变体反应中心，每个包含一个变化的氨基酸残基附近的细菌叶绿素二聚体。突变反应中心的光谱与野生型相似，并能够在光激发细菌叶绿素二聚体后将电子转移到醌类。他们表现出大范围的质子释放的程度和在连续照明后的氧化二聚体的光信号的缓慢恢复。六个氨基酸残基，Thr L130，Asp L155，Ser L244，Arg M164，Ser M190和His M193，显示了关键作用。分析结果指出，氢键网络，包含这些残基，与几个额外的残基和结合水分子，形成质子转移途径。除了质子转移，提出的路径的属性是负责连续照明后观察到的非常缓慢的电荷重组动力学。该途径的特点进行了比较，质子转移途径附近的仲醌，以及那些发现在光系统II和细胞色素c氧化酶。
Insight into control of proton transfer, a crucial attribute of cellular functions, can be gained from investigations of bacterial reaction centers. While the uptake of protons associated with the reduction of the quinone is well characterized, the release of protons associated with the oxidized bacteriochlorophyll dimer has been poorly understood. Optical spectroscopy and proton release/uptake measurements were used to examine the proton release characteristics of twelve mutant reaction centers, each containing a change in an amino acid residue near the bacteriochlorophyll dimer. The mutant reaction centers had optical spectra similar to wild-type and were capable of transferring electrons to the quinones after light excitation of the bacteriochlorophyll dimer. They exhibited a large range in the extent of proton release and in the slow recovery of the optical signal for the oxidized dimer upon continuous illumination. Key roles were indicated for six amino acid residues, Thr L130, Asp L155, Ser L244, Arg M164, Ser M190, and His M193. Analysis of the results points to a hydrogen-bond network that contains these residues, with several additional residues and bound water molecules, forming a proton transfer pathway. In addition to proton transfer, the properties of the pathway are proposed to be responsible for the very slow charge recombination kinetics observed after continuous illumination. The characteristics of this pathway are compared to proton transfer pathways near the secondary quinone as well as those found in photosystem II and cytochrome c oxidase.