Davis-Kaplan S R, Askwith C C, Bengtzen A C, Radisky D, Kaplan J
Division of Immunology and Cell Biology, Department of Pathology, School of Medicine, University of Utah, Salt Lake City, UT 84132, USA.
Proc Natl Acad Sci U S A. 1998 Nov 10;95(23):13641-5. doi: 10.1073/pnas.95.23.13641.
GEF1 is a gene in Saccharomyces cerevisiae, which encodes a putative voltage-regulated chloride channel. gef1 mutants have a defect in the high-affinity iron transport system, which relies on the cell surface multicopper oxidase Fet3p. The defect is due to an inability to transfer Cu+ to apoFet3p within the secretory apparatus. We demonstrate that the insertion of Cu into apoFet3p is dependent on the presence of Cl-. Cu-loading of apoFet3p is favored at acidic pH, but in the absence of Cl- there is very little Cu-loading at any pH. Cl- has a positive allosteric effect on Cu-loading of apoFet3p. Kinetic studies suggest that Cl- may also bind to Fet3p and that Cu+ has an allosteric effect on the binding of Cl- to the enzyme. Thus, Cl- may be required for the metal loading of proteins within the secretory apparatus. These results may have implications in mammalian physiology, as mutations in human intracellular chloride channels result in disease.
GEF1是酿酒酵母中的一个基因，它编码一种假定的电压调节氯离子通道。gef1突变体在高亲和力铁转运系统中存在缺陷，该系统依赖于细胞表面的多铜氧化酶Fet3p。这种缺陷是由于无法在分泌装置内将Cu+转移到脱辅基Fet3p上。我们证明，将Cu插入脱辅基Fet3p依赖于Cl-的存在。脱辅基Fet3p的铜负载在酸性pH值时更有利，但在没有Cl-的情况下，在任何pH值下铜负载都很少。Cl-对脱辅基Fet3p的铜负载有正变构效应。动力学研究表明，Cl-也可能与Fet3p结合，并且Cu+对Cl-与该酶的结合有别构效应。因此，Cl-可能是分泌装置内蛋白质金属负载所必需的。这些结果可能对哺乳动物生理学有影响，因为人类细胞内氯离子通道的突变会导致疾病。
