Brickner D G, Harada J J, Olsen L J
Department of Biology, University of Michigan, Ann Arbor 48109-1048, USA.
Plant Physiol. 1997 Apr;113(4):1213-21. doi: 10.1104/pp.113.4.1213.
Peroxisome biogenesis requires that proteins be transported from their site of synthesis in the cytoplasm to their final location in the peroxisome matrix or membrane. Glyoxysomes are a class of peroxisomes found primarily in germinating seedlings and are involved in mobilizing fatty acids via the glyoxylate cycle and the beta-oxidation pathway. We have used an in vitro assay to study the mechanism(s) of import of proteins into glyoxysomes. Results from this assay indicate that the transport process is time- and temperature-dependent and is specific for peroxisomal proteins. Isocitrate lyase, a glyoxysomal protein, and the leaf-type peroxisomal enzyme glycolate oxidase (GLO) were transported into pumpkin (Cucurbita pepo) glyoxysomes with no apparent differences in efficiency of import. Thus, this in vitro assay appears to be physiologically relevant and correlates well with expected in vivo conditions. Protein import was also energy-dependent and saturable. Nonradiolabeled GLO competed with radiolabeled, in vitro-synthesized GLO for components of the import machinery. Finally, pretreatment of the isolated glyoxysomes with protease virtually abolished subsequent import of GLO. Taken together, these results indicate that a proteinaceous receptor is involved in the import of peroxisomal proteins.
过氧化物酶体的生物发生要求蛋白质从其在细胞质中的合成位点转运至过氧化物酶体基质或膜中的最终位置。乙醛酸循环体是一类主要存在于萌发幼苗中的过氧化物酶体，通过乙醛酸循环和β-氧化途径参与脂肪酸的动员。我们利用体外测定法研究蛋白质导入乙醛酸循环体的机制。该测定法的结果表明，转运过程具有时间和温度依赖性，且对过氧化物酶体蛋白具有特异性。异柠檬酸裂解酶（一种乙醛酸循环体蛋白）和叶型过氧化物酶体酶乙醇酸氧化酶（GLO）被转运至南瓜（西葫芦）乙醛酸循环体中，导入效率无明显差异。因此，这种体外测定法似乎具有生理相关性，且与预期的体内条件相关性良好。蛋白质导入也是能量依赖性且可饱和的。未标记的GLO与放射性标记的体外合成GLO竞争导入机制的组分。最后，用蛋白酶预处理分离的乙醛酸循环体几乎完全消除了随后GLO的导入。综上所述，这些结果表明一种蛋白质受体参与过氧化物酶体蛋白的导入。
