Bishop Cleo L, Ulas Simin, Baena-Gonzalez Elena, Aro Eva-Mari, Purton Saul, Nugent Jonathan H A, Mäenpää Pirkko
Photosynthesis Research Group, Department of Biology, University College London, Darwin Building, Gower Street, London, WC1E 6BT, UK.
Photosynth Res. 2007 Jul-Sep;93(1-3):139-47. doi: 10.1007/s11120-007-9182-0. Epub 2007 May 22.
The psbZ gene of Synechocystis sp. PCC 6803 encodes the approximately 6.6 kDa photosystem II (PSII) subunit. We here report biophysical, biochemical and in vivo characterization of Synechocystis sp. PCC 6803 mutants lacking psbZ. We show that these mutants are able to perform wild-type levels of light-harvesting, energy transfer, PSII oxygen evolution, state transitions and non-photochemical quenching (NPQ) under standard growth conditions. The mutants grow photoautotrophically; however, their growth rate is clearly retarded under low-light conditions and they are not capable of photomixotrophic growth. Further differences exist in the electron transfer properties between the mutants and wild type. In the absence of PsbZ, electron flow potentially increased through photosystem I (PSI) without a change in the maximum electron transfer capacity of PSII. Further, rereduction of P700(+) is much faster, suggesting faster cyclic electron flow around PSI. This implies a role for PsbZ in the regulation of electron transfer, with implication for photoprotection.
集胞藻6803（Synechocystis sp. PCC 6803）的psbZ基因编码约6.6 kDa的光系统II（PSII）亚基。我们在此报告了缺乏psbZ的集胞藻6803突变体的生物物理、生化及体内特性。我们发现，这些突变体在标准生长条件下能够进行与野生型水平相当的光捕获、能量转移、PSII放氧、状态转换及非光化学猝灭（NPQ）。这些突变体能够进行光合自养生长；然而，在弱光条件下其生长速率明显减慢，且无法进行光合混合营养生长。突变体与野生型之间在电子传递特性方面还存在其他差异。在没有PsbZ的情况下，通过光系统I（PSI）的电子流可能增加，而PSII的最大电子传递能力没有变化。此外，P700(+)的再还原要快得多，这表明围绕PSI的循环电子流更快。这意味着PsbZ在电子传递调节中发挥作用，对光保护有影响。
