Wood J M
Proc Natl Acad Sci U S A. 1987 Jan;84(2):373-7. doi: 10.1073/pnas.84.2.373.
The PutA protein, product of the Escherichia coli gene putA, has two functions essential for proline utilization and for the regulation of putP and putA expression: as the peripheral membrane flavoprotein, proline dehydrogenase (EC 1.5.99.8), it transfers electrons from proline to the respiratory chain, and, as a repressor, it controls expression of genes putP and putA in response to proline supply. Association of proline dehydrogenase with the membrane was shown to require the simultaneous presence of the soluble enzyme, membranes, and proline. The kinetics of that association, monitored by following proline oxidation in a coupled enzyme assay system, were not altered when the transmembrane proton gradient generated during proline oxidation was dissipated by a proton ionophore. However, D-lactate or NADH could replace proline as a promoter of proline dehydrogenase-membrane association under anaerobic reaction conditions. These data imply that reduction of proline dehydrogenase and/or a membrane constituent promotes enzyme-membrane association. A biochemical mechanism is suggested whereby the concentration of proline dehydrogenase associated with the respiratory chain would be determined by proline supply.
大肠杆菌putA基因的产物PutA蛋白具有脯氨酸利用以及putP和putA表达调控所必需的两种功能：作为外周膜黄素蛋白脯氨酸脱氢酶（EC 1.5.99.8），它将电子从脯氨酸传递到呼吸链；作为阻遏物，它根据脯氨酸供应情况控制putP和putA基因的表达。脯氨酸脱氢酶与膜的结合被证明需要可溶性酶、膜和脯氨酸同时存在。在偶联酶分析系统中通过跟踪脯氨酸氧化来监测这种结合的动力学，当脯氨酸氧化过程中产生的跨膜质子梯度被质子离子载体消散时，其动力学并未改变。然而，在厌氧反应条件下，D-乳酸或NADH可以替代脯氨酸作为脯氨酸脱氢酶-膜结合的促进剂。这些数据表明脯氨酸脱氢酶和/或膜成分的还原促进了酶与膜的结合。本文提出了一种生化机制，据此与呼吸链相关的脯氨酸脱氢酶的浓度将由脯氨酸供应决定。
