Pesaresi P, Sandonà D, Giuffra E, Bassi R
Università di Verona, Facoltà di Scienze MM.FF.NN., Italy.
FEBS Lett. 1997 Feb 3;402(2-3):151-6. doi: 10.1016/s0014-5793(96)01518-9.
Energy-dependent quenching of chlorophyll fluorescence (qE) reflects the action of a powerful mechanism of protection from photoinhibition in which the low pH in the chloroplast lumen induces dissipation of excess excitation energy. Dicyclohexylcarbodiimide (DCCD), a protein-modifying agent, is a powerful inhibitor of qE and has been shown to react with acidic residues, in a hydrophobic environment, involved in proton translocation. The CP29 subunit of photosystem II has been proposed to be the site of qE quenching and shown to bind DCCD. We have hypothesised, on the basis of the CP29 protein sequence and of the structure of light-harvesting complex II protein, that glutamic acid 166 is the DCCD binding site. In this study, we have produced recombinant proteins either with wild-type sequence or carrying a mutation on the 166 position. We show that the mutant protein does not bind DCCD. This identifies E166 as the site whose protonation may lead to a conformational change triggering qE.
叶绿素荧光的能量依赖猝灭（qE）反映了一种强大的光抑制保护机制的作用，在这种机制中，叶绿体腔中的低pH值会导致过剩激发能的耗散。二环己基碳二亚胺（DCCD）是一种蛋白质修饰剂，是qE的强效抑制剂，已被证明能与参与质子转运的疏水环境中的酸性残基发生反应。光系统II的CP29亚基被认为是qE猝灭的位点，并已证明能结合DCCD。基于CP29蛋白序列和捕光复合物II蛋白的结构，我们推测谷氨酸166是DCCD结合位点。在这项研究中，我们制备了具有野生型序列或在166位携带突变的重组蛋白。我们发现突变蛋白不结合DCCD。这确定E166是其质子化可能导致构象变化从而触发qE的位点。
