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Sarcoplasmic reticulum release channels from frog skeletal muscle display two types of calcium dependence
Author(s) -
Bull Ricardo,
Marengo Juan José
Publication year - 1993
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(93)80341-q
Subject(s) - calcium , chemistry , endoplasmic reticulum , skeletal muscle , biophysics , calcium atpase , voltage dependent calcium channel , endocrinology , biochemistry , biology , enzyme , atpase , organic chemistry
Calcium channels derived from sarcoplasmic reticulum of frog skeletal muscle were fused with planar lipid bilayers. Fractional open times displayed two types of calcium dependence: (i) blockable channels showed a bell‐shaped calcium dependence with an activation constant of 4.5 μM, a Hill coefficient for activation of 1.46 and a blocking constant of 226 μM, and (ii) non‐blockable channels displayed a sigmoidal calcium dependence with an activation constant of 1.1 μM and a Hill coefficient of 1.42; no blocking effect was seen with calcium up to 0.5 mM. These two types of calcium dependence may underlie the coexistence of two different pathways for calcium release in frog skeletal muscle.