title: The topology of the cardiac Na⁺/Ca²⁺ exchanger, NCX1.
abstract: The topology of the plasma membrane Na(+)/Ca(2+) exchanger of cardiac muscle, NCX1, is uncertain. Biochemical analyses have indicated the presence of 9 transmembrane segments (TMSs) whereas the recent crystal structure of a prokaryotic homologue has 10 TMSs. The discrepancy is towards the C-terminus of the proteins where the prokaryotic homologue has an additional TMS8. To resolve this apparent disagreement, we re-assessed the topology of the C-terminal TMSs of NCX1. We examined the ability of internal or external cysteine residues in the N-terminal portion of NCX1 to crosslink with cysteine residues, of uncertain orientation, in the C-terminal portion of the protein. The results strongly support a model of NCX1 with 10 TMSs as found in the prokaryotic homologue.
authors: Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1760, USA.
authors: Xiaoyan
authors: X
authors: Ren
authors: Kenneth D
authors: KD
authors: Philipson
mesh_terms: D000818:Animals; D002460:Cell Line; D003432:Cross-Linking Reagents / Q000737:chemistry; D005026:Ethylene Glycols / Q000737:chemistry; D006801:Humans; D008958:Models, Molecular; D009036:Moths; D010618:Phenanthrolines / Q000737:chemistry; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D019831:Sodium-Calcium Exchanger / Q000737:chemistry*; D013886:Thiosulfonic Acids / Q000737:chemistry
chemical_list: D003432:Cross-Linking Reagents; D005026:Ethylene Glycols; D010618:Phenanthrolines; D019831:Sodium-Calcium Exchanger; D013886:Thiosulfonic Acids; C110374:sodium-calcium exchanger 1; C025205:1,10-phenanthroline
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