大肠杆菌对铷离子和钾离子的区分

Discrimination between Rb+ and K+ by Escherichia coli.

Rhoads D B, Woo A, Epstein W

Biochim Biophys Acta. 1977 Aug 15;469(1):45-51. doi: 10.1016/0005-2736(77)90324-8.

Abstract

The K+ requirment of Escherichia coli is only partially fulfilled by Rb+. The molar growth yield on Rb+ was about 5% of that on K+ and the growth rate in Rb+-supplemented media is lower thatn in K+ influx by any of the four K+ transport systems of E. coli. The high-affinity Kdp system (Km = 2 micron) is poorly traced by 86Rb+. It discriminates against a 86Rb+ tracer at least 1000-fold. The two moderate affinity systems, the high-rate TrkA system (Km = 1.5 mM) and the moderate rate TrkD system (Km = 0.5 mM), discriminate against a 86Rb+ tracer by approximately 10-fold and 25-fold, respectively. 86Rb+ is preferred by the low-rate TrkF system and overestimates its K+ influx by 40%.

摘要

大肠杆菌对钾离子的需求只有部分能被铷离子满足。以铷离子为营养源时的摩尔生长产量约为以钾离子为营养源时的5%，并且在添加铷离子的培养基中的生长速率低于在添加钾离子的培养基中的生长速率，这是由大肠杆菌的四种钾离子转运系统中的任何一种介导的钾离子内流所导致的。高亲和力的钾离子转运系统Kdp（Km = 2微摩尔）对86Rb+的摄取能力较差。它对86Rb+示踪剂的识别能力至少相差1000倍。两个中等亲和力的系统，即高速率的TrkA系统（Km = 1.5毫摩尔）和中速率的TrkD系统（Km = 0.5毫摩尔），对86Rb+示踪剂的识别能力分别相差约10倍和25倍。低速率的TrkF系统更倾向于摄取86Rb+，并且高估了其钾离子内流40%。