title: Characterization and purification of a Na+/Ca2+ exchanger from an archaebacterium.
abstract: The superfamily of cation/Ca(2+) exchangers includes both Na(+)/Ca(2+) exchangers (NCXs) and Na(+)/Ca(2+),K(+) exchangers (NCKX) as the families characterized in most detail. These Ca(2+) transporters have prominent physiological roles. For example, NCX and NCKX are important in regulation of cardiac contractility and visual processes, respectively. The superfamily also has a large number of members of the YrbG family expressed in prokaryotes. However, no members of this family have been functionally expressed, and their transport properties are unknown. We have expressed, purified, and characterized a member of the YrbG family, MaX1 from Methanosarcina acetivorans. MaX1 catalyzes Ca(2+) uptake into membrane vesicles. The Ca(2+) uptake requires intravesicular Na(+) and is stimulated by an inside positive membrane potential. Despite very limited sequence similarity, MaX1 is a Na(+)/Ca(2+) exchanger with kinetic properties similar to those of NCX. The availability of a prokaryotic Na(+)/Ca(2+) exchanger should facilitate structural and mechanistic investigations.
authors.affiliation: Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095-1751, USA.
authors.forename: Gabriel Mercado
authors.initials: GM
authors.lastname: Besserer
authors.forename: Debora A
authors.initials: DA
authors.lastname: Nicoll
authors.forename: Jeff
authors.initials: J
authors.lastname: Abramson
authors.forename: Kenneth D
authors.initials: KD
authors.lastname: Philipson
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D002462:Cell Membrane / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D017136:Ion Transport / Q000502:physiology; D008564:Membrane Potentials / Q000502:physiology; D017020:Methanosarcina / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012964:Sodium / Q000737:chemistry / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D019843:Archaeal Proteins; D011994:Recombinant Proteins; D019831:Sodium-Calcium Exchanger; D012964:Sodium; D002118:Calcium