Stemler A, Murphy J
Botany Department, University of California, Davis, California 95616.
Plant Physiol. 1985 Jan;77(1):179-82. doi: 10.1104/pp.77.1.179.
In maize chloroplasts, the ratio of HCO(3) (-) (anion) binding sites to high-affinity atrazine binding sites is unity. In the dark, atrazine noncompetitively inhibits the binding of half of the HCO(3) (-) to the photosystem II (PSII) complexes. The inhibition of binding saturates at 5 micromolar atrazine, little inhibition is seen at 0.5 micromolar atrazine, although the high-affinity herbicide binding sites are nearly filled at this concentration. This means that HCO(3) (-) and atrazine interact noncompetitively at a specific low-affinity herbicide binding site that exists on a portion of the PSII complexes. Light abolishes the inhibitory effects of atrazine on HCO(3) (-) binding. Based on the assumption that there is one high-affinity atrazine binding site per PSII complex, we conclude that there is also only one binding site for HCO(3) (-) with a dissociation constant near 80 micromolar. The location of the HCO(3) (-) binding site, and the low-affinity atrazine binding site, is not known.
在玉米叶绿体中，碳酸氢根离子（阴离子）结合位点与高亲和力莠去津结合位点的比例为1。在黑暗中，莠去津非竞争性抑制一半碳酸氢根离子与光系统II（PSII）复合物的结合。在5微摩尔莠去津时，结合抑制作用达到饱和，在0.5微摩尔莠去津时几乎没有抑制作用，尽管在此浓度下高亲和力除草剂结合位点几乎已被填满。这意味着碳酸氢根离子和莠去津在PSII复合物一部分上存在的特定低亲和力除草剂结合位点处非竞争性相互作用。光照消除了莠去津对碳酸氢根离子结合的抑制作用。基于每个PSII复合物有一个高亲和力莠去津结合位点的假设，我们得出结论，也只有一个碳酸氢根离子结合位点，其解离常数接近80微摩尔。碳酸氢根离子结合位点以及低亲和力莠去津结合位点的位置尚不清楚。
