TY - JOUR
T1 - Exchange of calcium between muscle Ca2+-binding proteins
AU - Moeschler, Hans J.
AU - Malencik, Dean A.
AU - Pocinwong, Sitivad
AU - Alaba, Olusola
AU - Kerrick, Glenn L.
AU - Fischer, Edmond H.
PY - 1979/9/10
Y1 - 1979/9/10
N2 - Sarcoplasmic reticulum isolated from skeletal muscle of the rabbit and the Pacific dogfish (Squalus acanthias) was characterized in terms of its Ca2+-uptake at different temperatures. SR from both species showed comparable Ca2+-uptake rates at their basal body temperatures (5°C and 37°C, respectively). Only very low percentages of phosphorylase, phosphorylase kinase and phosphatase were found to be associated with the purified vesicles, once these were freed of contaminating glycogen particles. Ca2+-fluxes during contraction/relaxation-cycles in muscles were studied in a reconstituted system by measuring the inhibition of the rate of Ca2+-uptake by the sarcoplasmic reticulum and of the Ca2+-dependent activity of phosphorylase kinase, respectively, by metal-free troponin, troponin-C, parvalbumin and phosphorylase kinase; EGTA was used as an internal standard. Ca2+-binding capacities of the various proteins were determined separately by gel filtration experiments. Data obtained agreed with published values for troponin, troponin-C and parvalbumin; for phosphorylase kinase, a value of n- = 8 was found regardless of the state of phosphorylation of the enzyme. Results obtained from both types of experiments established apparent Ca2+-affinities in the following decreasing order : phosphorylase kinase ∼ parvalbumin > EGTA > troponintroponin-C, with no difference found between the non-phosphorylated and phosphorylated forms of phosphorylase kinase. Apparent equilibrium constants for these Ca2+-complexes, relative to EGTA, were in agreement with published values obtained from classical equilibrium studies. Similar results were obtained with proteins isolated from rabbit and dogfish muscle. No indication of protein-protein interactions affecting Ca2+-fluxes could be found in such a reconstituted system, except for the singular case of a slight increased inhibition of phosphorylase kinase by parvalbumin following phosphorylation of the enzyme.
AB - Sarcoplasmic reticulum isolated from skeletal muscle of the rabbit and the Pacific dogfish (Squalus acanthias) was characterized in terms of its Ca2+-uptake at different temperatures. SR from both species showed comparable Ca2+-uptake rates at their basal body temperatures (5°C and 37°C, respectively). Only very low percentages of phosphorylase, phosphorylase kinase and phosphatase were found to be associated with the purified vesicles, once these were freed of contaminating glycogen particles. Ca2+-fluxes during contraction/relaxation-cycles in muscles were studied in a reconstituted system by measuring the inhibition of the rate of Ca2+-uptake by the sarcoplasmic reticulum and of the Ca2+-dependent activity of phosphorylase kinase, respectively, by metal-free troponin, troponin-C, parvalbumin and phosphorylase kinase; EGTA was used as an internal standard. Ca2+-binding capacities of the various proteins were determined separately by gel filtration experiments. Data obtained agreed with published values for troponin, troponin-C and parvalbumin; for phosphorylase kinase, a value of n- = 8 was found regardless of the state of phosphorylation of the enzyme. Results obtained from both types of experiments established apparent Ca2+-affinities in the following decreasing order : phosphorylase kinase ∼ parvalbumin > EGTA > troponintroponin-C, with no difference found between the non-phosphorylated and phosphorylated forms of phosphorylase kinase. Apparent equilibrium constants for these Ca2+-complexes, relative to EGTA, were in agreement with published values obtained from classical equilibrium studies. Similar results were obtained with proteins isolated from rabbit and dogfish muscle. No indication of protein-protein interactions affecting Ca2+-fluxes could be found in such a reconstituted system, except for the singular case of a slight increased inhibition of phosphorylase kinase by parvalbumin following phosphorylation of the enzyme.
UR - http://www.scopus.com/inward/record.url?scp=0018707459&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0018707459&partnerID=8YFLogxK
U2 - 10.1016/S0300-9084(79)80159-5
DO - 10.1016/S0300-9084(79)80159-5
M3 - Article
C2 - 115501
AN - SCOPUS:0018707459
VL - 61
SP - 615
EP - 624
JO - Biochimie
JF - Biochimie
SN - 0300-9084
IS - 5-6
ER -