Different Mechanisms of Energy Coupling for the Shock-sensitive and Shock-resistant Amino Acid Permeases of Escherichia coli

作者：Edward A. Berger, LEON A. HEPPEL · 发表于：Journal of Biological Chemistry · 年份：1974 · DOI：10.1016/s0021-9258(19)42031-0 · 被引用次数：340 · 研究领域：Protein Structure and Dynamics、Hemoglobin structure and function、Enzyme Structure and Function

Abstract Based on the effects of osmotic shock, two categories of transport systems have previously been shown to exist in gram-negative bacteria: (a) the shock-sensitive systems, which are associated with periplasmic binding proteins and which are absent from isolated membrane vesicles, and (b) the shock-insensitive systems, whose carrier proteins are not released by osmotic shock and which are active in membrane vesicles. In this extension of an earlier report (Berger, E. A. (1973) Proc. Nat. Acad. Sci. U. S. A. 70, 1514) energy coupling for several amino acid permeases was examined by studying the ability of various energy sources to drive uptake in starved Escherichia coli cells blocked at specific sites of energy metabolism. We conclude that the energy donors for the two classes of transport systems are fundamentally different. The following evidence suggests the obligatory requirement of phosphate bond energy for the shock-sensitive but not the shock-resistant permeases. (a) Mutants defective in the Ca, MgATPase cannot use oxidative energy supplied by d-lactate or phenazine methosulfate plus ascorbate to drive the shock-sensitive systems. The shock-resistant systems, however, are quite active with these electron donors. (b) Arsenate abolishes the activities of the shock-sensitive but not the shock-resistant permeases. (c) When supplied with a source of glycolytic ATP, the shock-sensitive systems in an ATPase mutant are quite active and are relatively resistant to anaero...