J Integr Plant Biol. ›› 2002, Vol. 44 ›› Issue (12): 1409-1417.

• Research Articles • Previous Articles     Next Articles

Theoretical Studies on the Mechanism of the Proton-transfer-coupled Electron Transfer Reactions Between Menaquinone QA and Ubiquinone QB in the Bacterial Photosynthetic Reaction Center of Rhodopseudomona viridis

MA Shu-Hua, XU Hong, ZHANG Ru-Bo, QU Zheng-Wang, ZHANG Xing-Kang and ZHANG Qi-Yuan   

  • Published:2002-12-21


The mechanism of the proton transfer coupled electron transfer (PT-ET) reactions between the menaquinone QA (MQ1) and ubiquinone QB (UQ1) in the bacterial photosynthetic reaction center of Rhodopseudomona viridis was studied by using the B3LYP/6-31G(d) method. The changes of standard Gibbs free energy ΔG0 of all possible reactions followed the ET reaction (1) were calculated. The results indicated that: (1) according to the ΔG0 values of corresponding reactions, UQ1 could not accept two electrons from MQ-1 continually without the coupled proton transfer reactions. Because of ΔG0 2b0, ΔG0 3b0 and ΔG04b0, the corresponding PT ET reactions could take place along with reactions (2b), (3b) and (4b) equentially; (2) on the gaseous condition, the first and second transferred protons (H+(1) and H+(2)) from the surrounding amino acid residues or water molecules will combine with the oxygen No.7 and oxygen No.8 of UQ1, respectively. On the condition of protein surroundings (by SCRF model,ε=4.0), the results are converse but the energy difference between the combination of H+(1) and H+(2) with UQ-1 is quite small. The difference of ΔG0 values between the corresponding reactions in gaseous surroundings and the SCRF model is not significant; (3) the PT ET reactions between MQ1-and UQ1-should be as follows: MQ1-+UQ1→MQ1+UQ1- (1) UQ1-(O(7)+H+(HisL190) →UQ1H (2b)(Gas) or UQ1-(O(8))+H+(H2O)→UQ1H (2b') (SCRF) or UQ1-(O(8))+H+ (ArgL217)→UQ1H (2b')(SCRF) MQ-+UQ1H→MQ1+UQ1H- (3b)(Gas) MQ1-+UQ1H→Q1+UQ1H- (3b') (SCRF) UQ1H-+H+(H2O)→UQ1H2 (4b)(Gas) or UQ1H-+H+ (ArgL217)→UQ1H2 (4b) (Gas) or UQ1H-+H+ (HisL190)→UQ1H2 (4b') (SCRF)

Rhodopseudomena viridis 细菌光合作用反应中心质体醌QA与泛醌QB间电子转移耦合质子转移机理的理论研究
马淑华 徐 红 张汝波 屈正旺 张兴康 张启元*


摘要:用量子化学B3LYP/ 6 - 31G(d)方法 ,对Rhodopseudomenaviridis细菌光合反应中心质体醌QA(MQ1)与泛醌QB(UQ1)间的电子转移耦合质子转移 (PT-ET)机理进行了研究。对反应 (1)之后的Gibbs自由能变化进行了计算。结果表明 ,(1)按照各反应的数值 ,在无耦合质子转移的情况下 ,UQ1不可能由MQ1连续接受两个电子。由于ΔG02b 0 ,ΔG03b 0和ΔG04b 0 ,相应的PT ET反应将依序沿 (2b)、(3b)及 (4b)进行。 (2 )在气相情况下 ,由于周围的氨基酸残基或水分子转移到UQ1的第一个及第二个质子 (H+ (1)和H+ (2 ) )将先后分别与UQ1的No.7和No .8氧原子结合 ;在蛋白环境情况下 (SCRF方法 ,ε =4 .0 ) ,质子耦合的顺序正相反 ,但H+ (1)和H+ (2 )与UQ-1结合的能量传递差很小。在气相及SCRF模拟环境中 ,相同反应间的ΔG0 无显著差别。 (3)MQ-1间UQ-1的PT ET反应如下 :  MQ1-+UQ1→MQ1+UQ1-(1)  UQ1-(O( 7) ) +H+ (HisL190 )→UQ1H (2b) (Gas)or UQ1-(O( 8) ) +H+ (H2 O)→UQ1H (2b’) (SCRF)or UQ1-(O( 8) ) +H+ (ArgL2 17)→UQ1H (2b’) (SCRF)  MQ1-+UQ1H→MQ1+UQ1H-(3b) (Gas)  MQ1-+UQ1H→MQ1+UQ1H-(3b’) (SCRF)  UQ1H-+H+ (H2 O)→UQ1H2 (4b) (Gas)or UQ1H-+H+ (ArgL2 17)→UQ1H2 (4b ) (Gas)or UQ1H-+H+ (HisL 190) →UQ1H2(4b ’)(SCRF)
关键词: Rhodopseudomena viridis ;电子转移;质子转移;QA和QB;DFT

通讯作者。Fax:+86 (0) 10 62588930;E-mail: zhangqy @ infoc3.icas.ac.cn.

Key words: Rhodopseudomena viridis, electron transfer, proton transfer, QA and QB;

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