Maffia M, Verri T, Danieli A, Thamotharan M, Pastore M, Ahearn G A, Storelli C
Dipartimento di Biologia, Università di Lecce, Italy.
Am J Physiol. 1997 Jan;272(1 Pt 2):R217-25. doi: 10.1152/ajpregu.1997.272.1.R217.
A plasma membrane H(+)-glycyl-L-proline (Gly-L-Pro) cotransport mechanism has been identified in isolated eel intestinal brush-border membrane vesicles (BBMV) by both measuring radiolabeled Gly-L-Pro uptake and monitoring Gly-L-Pro-dependent H+ influx with the pH-sensitive dye acridine orange. The application of an inside negative membrane potential resulted in increasing Gly-L-Pro uptake, as well as the application of inwardly directed H+ gradient (although only when an inside negative membrane potential was present). Furthermore, vesicular H+ influx was found specifically associated with the presence of Gly-L-Pro in the extravesicular medium. The carrier-mediated nature of H(+)-Gly-L-Pro cotransport was assessed, and its concentration that yielded one-half maximal Gly-L-Pro influx was approximately 1.30 mM when measured by either radioactive or fluorescent tracers. Different dipeptides strongly inhibited Gly-L-Pro uptake by eel intestinal BBMV, as well as the cephalosporin antibiotic cephalexin, suggesting that dipeptide molecules and cephalosporin antibiotics may share a common transport system in eel intestinal BBMV.
通过测量放射性标记的甘氨酰 - L - 脯氨酸（Gly - L - Pro）摄取以及用pH敏感染料吖啶橙监测Gly - L - Pro依赖性H⁺内流，在分离的鳗鱼肠道刷状缘膜囊泡（BBMV）中鉴定出一种质膜H⁺ - 甘氨酰 - L - 脯氨酸（Gly - L - Pro）共转运机制。施加膜内负电位会导致Gly - L - Pro摄取增加，施加内向H⁺梯度时也是如此（尽管只有在存在膜内负电位时）。此外，发现囊泡H⁺内流与囊泡外介质中Gly - L - Pro的存在特异性相关。评估了H⁺ - Gly - L - Pro共转运的载体介导性质，当通过放射性或荧光示踪剂测量时，产生最大Gly - L - Pro内流一半的其浓度约为1.30 mM。不同的二肽强烈抑制鳗鱼肠道BBMV对Gly - L - Pro的摄取，以及头孢菌素抗生素头孢氨苄，这表明二肽分子和头孢菌素抗生素可能在鳗鱼肠道BBMV中共享一个共同的转运系统。
