title: HRC (histidine-rich Ca2+ binding protein) resides in the lumen of sarcoplasmic reticulum as a multimer.
abstract: HRC (histidine-rich Ca2+ binding protein) has been identified from skeletal and cardiac muscle and shown to bind Ca2+ with low affinity and high capacity that is reminiscent of calsequestrin. The physiological role of HRC is largely unknown. In this study, we show that HRC exists as a multimeric complex (probably larger than a pentamer) under physiological conditions. At higher Ca2+ concentrations, the complex appeared to dissociate into dimers or trimers that form a more relaxed structure. This is in striking contrast to the characteristics of calsequestrin. An earlier immuno-electron microscopic study showed that HRC resides in the lumen of the sarcoplasmic reticulum (SR), but this conclusion has been challenged by other data. By tryptic digestion and biotinylation of SR vesicles, we provide compelling evidence showing that HRC is indeed present in the lumen of the SR.
authors.affiliation: Department of Life Science, Kwangju Institute of Science and Technology, Kwangju, 500-712, Korea.
authors.forename: J Y
authors.initials: JY
authors.lastname: Suk
authors.forename: Y S
authors.initials: YS
authors.lastname: Kim
authors.forename: W J
authors.initials: WJ
authors.lastname: Park
mesh_terms: D000818:Animals; D019921:Biotinylation; D002135:Calcium-Binding Proteins / Q000737:chemistry* / Q000302:isolation & purification; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D046911:Macromolecular Substances; D008970:Molecular Weight; D009124:Muscle Proteins / Q000737:chemistry* / Q000302:isolation & purification; D018482:Muscle, Skeletal / Q000737:chemistry*; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000737:chemistry*; D014357:Trypsin
chemical_list: D002135:Calcium-Binding Proteins; C489419:HRC protein, Oryctolagus cuniculus; D046911:Macromolecular Substances; D009124:Muscle Proteins; D010446:Peptide Fragments; D014357:Trypsin