Impact of mutations within the putative Ca2+-binding lumenal interhelical a-b loop of the photosystem II D1 protein on the kinetics of photoactivation and H2O-oxidation in Synechocystis sp. PCC6803.
Impact of mutations within the putative Ca2+-binding lumenal interhelical a-b loop of the photosystem II D1 protein on the kinetics of photoactivation and H2O-oxidation in Synechocystis sp. PCC6803.
复制标题
光系统 II D1 蛋白的假定 Ca2 结合腔内螺旋 a-b 环内的突变对集胞藻中光活化和 H2O 氧化动力学的影响。
DOI：
10.1021/bi982331i
复制
发表时间：
1999
期刊：
影响因子：
--
通讯作者：
Burnap,RL
中科院分区：
文献类型：
--
作者：
Qian,M;Dao,L;Debus,RJ;Burnap,RL
Mutations D1−D59N and D1−D61E in the putative Ca2+-binding lumenal interhelical a−b loop of the photosystem II (PSII) D1 protein [Chu, H. A., Nguyen, A. P., and Debus (1995),Biochemistry34, 5839−5858] were further characterized in terms of S-state cycling and photoactivation. Bare platinum electrode measurements of centrifugally deposited O2-evolving membranes isolated from the a−b loop mutants demonstrated a retarded appearance of O2following single turnover flashes, although not to the extent of retardation seen in the Δpsb0 mutant, which lacks the extrinsic manganese-stabilizing protein (MSP). Double flash measurements indicate that retarded O2release in mutants coincides with a decrease in overall PSII turnover during the S3-[S4]-S0transition. S2and S3decay measurements in the isolated membranes indicate that D1−D59N and D1−D61E have faster decays of these higher S-states in contrast to slowed decays in the Δpsb0 mutant. Measurements of the flash interval dependence of photoactivation indicate that intermediates of photoactivation [light-dependent assembly of the (Mn)4complex] are highly destabilized in the a−b loop mutants compared to both ΔpsbO and the wild-type: flash intervals of greater than 2 s result in the nearly complete decay of unstable photointermediate(s) in the D1−D59N and D1−D61E samples, whereas a similar loss does not occur until intervals even greater than 10 s in the ΔpsbO and wild-type samples. These results are consistent with a role for the residues D1−D59 and D1−D61 in modulating the redox properties of the higher S-states and, also, possibly in the binding the calcium ion involved in photoactivation.
