Unique topology of the internal repeats in the cardiac Na+/Ca2+ exchanger

FEBS Letters

Nakamura, Tomoe Y²  Uehara, Akira¹  Iwamoto, Takahiro²  Imanaga, Issei¹  Shigekawa, Munekazu²  Pan, Yan² 

[1] Department of Physiology, School of Medicine, Fukuoka University, Fukuoka 814-0180, Japan;Department of Molecular Physiology, National Cardiovascular Center Research Institute, Suita, Osaka 565-8565, Japan

关键词: Na+/Ca2+ exchanger;    Membrane topology;    Cysteine susceptibility analysis;    Epitope tagging;   

DOI  :  10.1016/S0014-5793(99)00218-5

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

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 α-1 and α-2 repeats. Unexpectedly, we found that the connecting loop in the α-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 α-2 repeat is mostly accessible from the cytoplasm. Together with other data, we propose that the exchanger may consist of nine transmembrane helices.

【 授权许可】

Unknown