Kim M, Christopher D A, Mullet J E
Department of Biochemistry and Biophysics, Crop Biotechnology Center, Texas A&M University, College Station, Texas 77843, USA.
Plant Physiol. 1999 Feb;119(2):663-70. doi: 10.1104/pp.119.2.663.
The chloroplast gene psbD encodes D2, a chlorophyll-binding protein located in the photosystem II reaction center. Transcription of psbD in higher plants involves at least three promoters, one of which is regulated by blue light. The psbD blue-light-regulated promoter (BLRP) consists of a -10 promoter element and an activating complex, AGF, that binds immediately upstream of -35. A second sequence-specific DNA-binding complex, PGTF, binds upstream of AGF between -71 and -100 in the barley (Hordeum vulgare) psbD BLRP. In this study we report that ADP-dependent phosphorylation selectively inhibits the binding of PGTF to the barley psbD BLRP. ATP at high concentrations (1-5 mM) inhibits PGTF binding, but in the presence of phosphocreatine and phosphocreatine kinase, this capacity is lost, presumably due to scavenging of ADP. ADP inhibits PGTF binding at relatively low concentrations (0.1 mM), whereas other nucleotides are unable to mediate this response. ADP-mediated inhibition of PGTF binding is reduced in the presence of the protein kinase inhibitor K252a. This and other results suggest that ADP-dependent phosphorylation of PGTF (or some associated protein) inhibits binding of PGTF to the psbD BLRP and reduces transcription. ADP-dependent phosphorylation is expected to increase in darkness in parallel with the rise in ADP levels in chloroplasts. ADP-dependent phosphorylation in chloroplasts may, therefore, in coordination, inactivate enzymes involved in carbon assimilation, protein synthesis, and transcription during diurnal light/dark cycles.
叶绿体基因psbD编码D2，一种位于光系统II反应中心的叶绿素结合蛋白。高等植物中psbD的转录涉及至少三个启动子，其中一个受蓝光调控。psbD蓝光调控启动子（BLRP）由一个-10启动子元件和一个激活复合物AGF组成，AGF紧挨着-35上游结合。第二个序列特异性DNA结合复合物PGTF，在大麦（Hordeum vulgare）psbD BLRP中，于AGF上游-71至-100之间结合。在本研究中，我们报告ADP依赖性磷酸化选择性抑制PGTF与大麦psbD BLRP的结合。高浓度（1-5 mM）的ATP抑制PGTF结合，但在有磷酸肌酸和磷酸肌酸激酶存在时，这种能力丧失，推测是由于ADP被清除。ADP在相对低浓度（0.1 mM）时抑制PGTF结合，而其他核苷酸则无法介导这种反应。在蛋白激酶抑制剂K252a存在时，ADP介导的PGTF结合抑制作用减弱。这一结果及其他结果表明，PGTF（或某些相关蛋白）的ADP依赖性磷酸化抑制PGTF与psbD BLRP的结合并减少转录。预计在黑暗中，随着叶绿体中ADP水平的升高，ADP依赖性磷酸化也会增加。因此，叶绿体中的ADP依赖性磷酸化可能在昼夜光/暗循环中协同使参与碳同化、蛋白质合成和转录的酶失活。
