Referenced in: none

Automatically associated channels: Kv10.1 , Kv2.1

Title: Further characterization of the type 3 ryanodine receptor (RyR3) purified from rabbit diaphragm.

Authors: T Murayama, T Oba, E Katayama, H Oyamada, K Oguchi, M Kobayashi, K Otsuka, Y Ogawa

Journal, date & volume: J. Biol. Chem., 1999 Jun 11 , 274, 17297-308

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/10358090

Abstract
We characterized type 3 ryanodine receptor (RyR3) purified from rabbit diaphragm by immunoaffinity chromatography using a specific antibody. The purified receptor was free from 12-kDa FK506-binding protein, although it retained the ability to bind 12-kDa FK506-binding protein. Negatively stained images of RyR3 show a characteristic rectangular structure that was indistinguishable from RyR1. The location of the D2 segment, which exists uniquely in the RyR1 isoform, was determined as the region around domain 9 close to the corner of the square-shaped assembly, with use of D2-directed antibody as a probe. The RyR3 homotetramer had a single class of high affinity [3H]ryanodine-binding sites with a stoichiometry of 1 mol/mol. In planar lipid bilayers, RyR3 displayed cation channel activity that was modulated by several ligands including Ca2+, Mg2+, caffeine, and ATP, which is consistent with [3H]ryanodine binding activity. RyR3 showed a slightly larger unit conductance and a longer mean open time than RyR1. Whereas RyR1 showed two classes of channel activity with distinct open probabilities (Po), RyR3 displayed a homogeneous and steeply Ca2+-dependent activity with Po approximately 1. RyR3 was more steeply affected in the channel activity by sulfhydryl-oxidizing and -reducing reagents than RyR1, suggesting that the channel activity of RyR3 may be transformed more precipitously by the redox state. This is also a likely explanation for the difference in the Ca2+ dependence of RyR3 between [3H]ryanodine binding and channel activity.