a Department of Mathematical and Life Sciences , Graduate School of Science, Hiroshima University , Kagamiyama, Higashi-Hiroshima , Hiroshima , Japan.
Plant Signal Behav. 2017 Apr 3;12(4):e1304342. doi: 10.1080/15592324.2017.1304342.
Treatment of isolated Arabidopsis thaliana thylakoid membranes with nitrogen dioxide (NO) induces selective nitration of the tyrosine residue at the ninth amino acid (Tyr) of PsbO1. This selective nitration is triggered by light and is inhibited by photosynthetic electron transport inhibitors. Therefore, we postulated that, similar to Tyr of D1 (Y), Tyr of PsbO1 is redox active and is selectively oxidized by photosynthetic electron transport in response to illumination to a tyrosyl radical that is highly susceptible to nitration. This tyrosyl radical may combine rapidly at diffusion-controlled rates with NO to form 3-nitrotyrosine. If this postulation is correct, the nitration of Tyr of PsbO1 should decrease oxygen evolution activity. We investigated the effects of PsbO1 nitration on oxygen evolution from isolated thylakoid membranes, and found that nitration decreased oxygen evolution to ≥ 0% of the control. Oxygen evolution and nitration were significantly negatively correlated. This finding is consistent with redox active properties of the Tyr gene of PsbO1, and suggests that PsbO1 Tyr acts as an electron relay, such as Y in the photosystem II oxygenic electron transport chain.
用二氧化氮（NO）处理分离的拟南芥类囊体膜会诱导 PsbO1 第 9 位氨基酸（Tyr）的酪氨酸残基发生选择性硝化。这种选择性硝化是由光触发的，并被光合电子传递抑制剂抑制。因此，我们假设，类似于 D1 的 Tyr（Y），PsbO1 的 Tyr 是氧化还原活性的，并且在光照下通过光合电子传递被选择性氧化为对硝化高度敏感的酪氨酸自由基。这个酪氨酸自由基可能会以扩散控制的速率与 NO 迅速结合形成 3-硝基酪氨酸。如果这个假设是正确的，那么 PsbO1 的 Tyr 硝化应该会降低氧的产生活性。我们研究了 PsbO1 硝化对分离的类囊体膜中氧产生的影响，发现硝化会使氧产生降低至≤对照的 0%。氧的产生和硝化呈显著负相关。这一发现与 PsbO1 Tyr 的氧化还原活性一致，并表明 PsbO1 Tyr 作为电子中继体起作用，例如在光合系统 II 放氧电子传递链中的 Y。
