Oliver D J, Raman R
Department of Molecular Biology and Biochemistry, University of Idaho, Moscow 83843, USA.
J Bioenerg Biomembr. 1995 Aug;27(4):407-14. doi: 10.1007/BF02110003.
The four component proteins of the glycine decarboxylase multienzyme complex (the P-, H-, T-, and L-proteins) comprise over one-third of the soluble proteins in mitochondria isolated from the leaves of C3 plants. Together with serine hydroxymethyltransferase, glycine decarboxylase converts glycine to serine and is the site of photorespiratory CO2 and NH3 release. The component proteins of the complex are encoded on nuclear genes with N-terminal presequences that target them to the mitochondria. The isolated complex readily dissociates into its component proteins and reassociates into the intact complex in vitro. Because of the intimate association between photosynthesis and photorespiration, the proteins of the complex are present at higher levels in leaves in the light. The expression of these genes is controlled at the transcriptional level and the kinetics of expression are closely related to those of the small subunit of Rubisco. Deletion analysis of fusions between the promoter of the H-protein of the complex and the reporter gene beta-glucuronidase in transgenic tobacco has identified a region responsible for the tissue specificity and light dependence of gene expression. Gel shift experiments show that a nuclear protein in leaves binds to this region. Glycine decarboxylase has proven to be an excellent system for studying problems in plant biochemistry ranging from protein-protein interactions to control of gene expression.
甘氨酸脱羧酶多酶复合体的四种组成蛋白（P蛋白、H蛋白、T蛋白和L蛋白）占从C3植物叶片中分离出的线粒体可溶性蛋白的三分之一以上。甘氨酸脱羧酶与丝氨酸羟甲基转移酶一起，将甘氨酸转化为丝氨酸，是光呼吸过程中释放二氧化碳和氨的部位。该复合体的组成蛋白由核基因编码，其N端前序列将它们靶向线粒体。分离出的复合体很容易解离成其组成蛋白，并在体外重新组装成完整的复合体。由于光合作用和光呼吸之间的密切联系，该复合体的蛋白在叶片中光照条件下含量更高。这些基因的表达在转录水平受到控制，其表达动力学与核酮糖-1,5-二磷酸羧化酶小亚基的表达动力学密切相关。在转基因烟草中，对该复合体H蛋白启动子与报告基因β-葡萄糖醛酸酶的融合体进行缺失分析，确定了一个负责基因表达的组织特异性和光依赖性的区域。凝胶迁移实验表明，叶片中的一种核蛋白与该区域结合。事实证明，甘氨酸脱羧酶是研究从蛋白质-蛋白质相互作用到基因表达调控等植物生物化学问题的优秀系统。
