Wolber P K, Eilmann M, Steinback K E
Arch Biochem Biophys. 1986 Jul;248(1):224-33. doi: 10.1016/0003-9861(86)90420-0.
A number of herbicide classes, including the s-triazines and ureas (atrazine, diuron) inhibit photosynthetic electron transport via a direct interaction with the QB-protein. This protein, also known as the 32-kDa protein or herbicide binding protein, is believed to bind the plastoquinone QB, which functions as the second stable electron acceptor at the reducing side of Photosystem II. The site of covalent attachment of the photoaffinity herbicide analog azido-[14C]atrazine to the QB-protein of spinach chloroplast thylakoid membranes has been determined. Two amino acid residues are labeled; one residue is methionine-214, the other lies between histidine-215 and arginine-225. Both residues are within a region of the amino acid sequence which is highly conserved between the QB-protein and the L and M reaction center proteins of Rhodopseudomonas capsulata and R. sphaeroides. This region includes the site of a mutation which results in diuron resistance in Chlamydomonas reinhardi (valine-219). However, this region is well removed from point mutations at phenylalanine-255 (which gives rise to atrazine resistance in C. reinhardi) and at serine-264, (which results in extreme atrazine resistance in C. reinhardi and naturally occurring weed biotypes). The patterns of labeling and mutation imply that the quinone and herbicide binding site is formed by at least two protein domains.
包括均三嗪类和脲类（莠去津、敌草隆）在内的一些除草剂类别，通过与QB蛋白直接相互作用来抑制光合电子传递。该蛋白也被称为32 kDa蛋白或除草剂结合蛋白，据信它能结合质体醌QB，而质体醌QB在光系统II的还原侧作为第二个稳定的电子受体发挥作用。已经确定了光亲和性除草剂类似物叠氮基-[14C]莠去津与菠菜叶绿体类囊体膜的QB蛋白共价连接的位点。有两个氨基酸残基被标记；一个残基是甲硫氨酸-214，另一个位于组氨酸-215和精氨酸-225之间。这两个残基都在氨基酸序列的一个区域内，该区域在QB蛋白与荚膜红假单胞菌和球形红假单胞菌的L和M反应中心蛋白之间高度保守。该区域包括一个突变位点，该突变会导致莱茵衣藻产生敌草隆抗性（缬氨酸-219）。然而，该区域与苯丙氨酸-255（导致莱茵衣藻产生莠去津抗性）和丝氨酸-264（导致莱茵衣藻以及天然存在的杂草生物型产生极端莠去津抗性）的点突变位置相距较远。标记和突变模式表明，醌和除草剂结合位点是由至少两个蛋白质结构域形成的。
