Bochkareva E S, Solovieva M E, Girshovich A S
Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, Israel.
Proc Natl Acad Sci U S A. 1998 Jan 20;95(2):478-83. doi: 10.1073/pnas.95.2.478.
Chaperonin GroEL has been found to interact with isolated cytoplasmic membrane of Escherichia coli. Interaction requires Mg ions, whereas MgATP inhibits, and inhibition is stronger in the presence of co-chaperonin GroES. "Heat-shock" of the membrane at 45 degrees C destroys irreversibly its ability to bind GroEL. The binding of GroEL is characterized by saturation with a maximum of about 100 pmol GroEL bound per mg of total membrane protein, indicating a limited capacity and specificity of the membrane to bind GroEL. According to results of immunoblotting analysis and cleavable photoactivable cross-linking, a membrane target of GroEL is SecA, a protein known as a central component of the translocation machinery. Moreover, in some cases GroEL could modulate a cycle of association of SecA with the membrane by stimulating release of SecA from the membrane. A physiological role of targeting of GroEL in or close to the protein-conducting membrane apparatus is discussed.
伴侣蛋白GroEL已被发现可与大肠杆菌分离的细胞质膜相互作用。这种相互作用需要镁离子，而MgATP则起抑制作用，并且在有共伴侣蛋白GroES存在时抑制作用更强。在45摄氏度对膜进行“热休克”会不可逆地破坏其结合GroEL的能力。GroEL的结合具有饱和性，每毫克总膜蛋白最多结合约100皮摩尔GroEL，这表明膜结合GroEL的能力和特异性有限。根据免疫印迹分析和可切割的光活化交联结果，GroEL的一个膜靶点是SecA，一种已知为转运机制核心成分的蛋白质。此外，在某些情况下，GroEL可通过刺激SecA从膜上释放来调节SecA与膜的结合循环。本文讨论了GroEL靶向蛋白质传导膜装置内部或附近的生理作用。
