Abstract
Sodium/calcium exchangers are membrane transporters which play an important role in calcium homeostasis by removing calcium out of the cell using the sodium gradient as driving force. This is essential for cell signaling as well as muscle activity and other functions. Recently NCx from Methanococcus jannaschii (NCx_Mj) has been crystalized and a structure model has been proposed.Here we show direct functional measurements of this transporter obtained by surface supported membrane technology. The experiments were performed on the SURFE2R device (SURFace Electrogenic Event Reader, Nanion Technologies). Therefore we reconstituted bacterial NCx into lipid vesicles which were then accumulated on a lipid coated gold surface. Due to rapid addition and removal of substrate ions NCx activity could be evoked.We characterized substrate dependency of sodium and calcium and their interactions. Competing substrates like potassium and magnesium were investigated on their interfering behavior. The results were compared to human NCx in membrane fragments.View Large Image | View Hi-Res Image | Download PowerPoint Slide
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