CALCIUM-TRANSPORT MEDIATED BY NHAA, A NA+/H+ ANTIPORTER FROM ESCHERICHIA-COLI
CALCIUM-TRANSPORT MEDIATED BY NHAA, A NA+/H+ ANTIPORTER FROM ESCHERICHIA-COLI
复制标题
DOI：
10.1016/0014-5793(93)80870-z
复制
发表时间：
1993-12-28
期刊：
影响因子：
3.5
通讯作者：
DIBROV, PA
中科院分区：
文献类型：
--
作者：
DIBROV, PA
在只有一个Na+/H+逆向转运蛋白(NhaA)的E.ColiEP432/pGM42株的翻转膜小泡中，外源CaCl2抑制呼吸相关的Delta pH的消散，并降低囊泡内Na+的平衡浓度。在NhaA蛋白脂质体中，施加人工Delta pH(内部是酸)会导致钙的几倍积累。在pH 8.5时，Delta pH驱动的钙吸收的表观K-m为2 mM，V-max为1.79mU·mol/min/mg蛋白质。Delta pH的消散会导致小泡中钙的释放。CaCl2可抑制重组NhaA介导的Delta pH驱动的Na+摄取，反之亦然。此外，在含有nhaA的蛋白脂质体中还发现了异质性的钙/钠交换。跨膜电位差被证明驱动了这一过程。这些数据与NhaA也能催化钙/氢交换的假设是一致的。
In everted membrane vesicles of E. coli strain EP432/pGM42, which has only one Na+/H+ antiporter (NhaA), external CaCl2 inhibits dissipation of the respiration-dependent Delta pH in response to the addition of NaCl at pH 7.5, and decreases equilibrium concentration of the intravesicular Na+. In the NhaA proteoliposomes, imposition of an artificial Delta pH (acid inside) leads to the several-fold accumulation of calcium. The apparent K-m for this Delta pH-driven Ca2+ uptake at pH 8.5 is 2 mM, and the V-max is 1.79 mu mol/min/mg of protein. Dissipation of Delta pH causes release of calcium from the vesicles. CaCl2 was found to inhibit the Delta pH-driven Na+ uptake mediated by reconstituted NhaA, and vice versa. Further, heterological Ca2+/Na+ exchange has been demonstrated in proteoliposomes containing NhaA. Transmembrane electric potential difference proved to drive this process. All these data are consistent with the assumption that NhaA can also catalyze Ca2+/H+ exchange.