Iwamoto T, Nakamura T Y, Pan Y, Uehara A, Imanaga I, Shigekawa M
Department of Molecular Physiology, National Cardiovascular Center Research Institute, Suita, Osaka, Japan.
FEBS Lett. 1999 Mar 12;446(2-3):264-8. doi: 10.1016/s0014-5793(99)00218-5.
Hydropathy analysis predicts 11 transmembrane helices in the cardiac Na+/Ca2+ exchanger. Using cysteine susceptibility analysis and epitope tagging, we here studied the membrane topology of the exchanger, in particular of the highly conserved internal alpha-1 and alpha-2 repeats. Unexpectedly, we found that the connecting loop in the alpha-1 repeat forms a re-entrant membrane loop with both ends facing the extracellular side and one residue (Asn-125) being accessible from the inside and that the region containing the alpha-2 repeat is mostly accessible from the cytoplasm. Together with other data, we propose that the exchanger may consist of nine transmembrane helices.
亲水性分析预测心脏钠钙交换体中有11个跨膜螺旋。我们利用半胱氨酸敏感性分析和表位标签技术，在此研究了该交换体的膜拓扑结构，特别是高度保守的内部α-1和α-2重复序列的膜拓扑结构。出乎意料的是，我们发现α-1重复序列中的连接环形成了一个折返膜环，其两端都面向细胞外侧，且有一个残基（Asn-125）可从内部接触到，并且包含α-2重复序列的区域大多可从细胞质接触到。结合其他数据，我们提出该交换体可能由9个跨膜螺旋组成。
