scholarly journals Biological activities of the peptides obtained by digestion of troponin C and calmodulin with thrombin

1981 ◽  
Vol 195 (1) ◽  
pp. 307-316 ◽  
Author(s):  
C M Wall ◽  
R J A Grand ◽  
S V Perry
Keyword(s):  
Protein Kinase ◽  
Cyclic Amp ◽  
Myosin Light Chain Kinase ◽  
Myosin Light Chain ◽  
Troponin I ◽  
Biological Activities ◽  
Troponin C ◽  
Dependent Protein Kinase ◽  
Electrophoretic Mobilities ◽  
Dependent Protein

1. Troponin C and calmodulin were not digested by thrombin at a significant rate in the presence of Ca2+. 2. In the presence of EGTA, troponin C was digested by thrombin to yield three peptides, TH1 (residues 1--120), TH3 (residues 1--100) and TH2 (residues 121--159). 3. In the presence of EGTA calmodulin was digested by thrombin giving two peptides, TM1 (residues 1--106) and TM2 (residues 107--148). 4. The electrophoretic mobilities of peptides TH1 and TM1 were increased at pH 8.6 by Ca2+ both in the presence and absence of urea. The mobilities of peptides TH2 and TM2 were unaltered under these conditions. 5. Peptides TH1, TH2 and tM1 formed complexes with troponin I on polyacrylamide gels at pH 8.6 in the presence of Ca2+. 6. The phosphorylation of troponin I by cyclic AMP-dependent protein kinase was significantly inhibited by peptides TH1 and TH3 and to a lesser extent by peptide TM1. 7. The calmodulin peptide TM1 activated myosin light-chain kinase when present in large molar excess. Peptide TM2 did not activate the enzyme.

scholarly journals Phosphorylation of skeletal-muscle troponin I and troponin T by phospholipid-sensitive Ca2+-dependent protein kinase and its inhibition by troponin C and tropomyosin

1984 ◽  
Vol 218 (2) ◽  
pp. 361-369 ◽  
Author(s):  
G J Mazzei ◽  
J F Kuo
Keyword(s):  
Protein Kinase ◽  
Cyclic Amp ◽  
Cardiac Troponin ◽  
Troponin I ◽  
Troponin T ◽  
Troponin C ◽  
Cardiac Troponin I ◽  
Equimolar Amount ◽  
Dependent Protein Kinase ◽  
Dependent Protein

Skeletal-muscle troponin I and troponin T were found to be rapidly phosphorylated by cardiac phospholipid-sensitive Ca2+-dependent protein kinase, with Km values of 6.66 and 0.13 microM respectively. Stoichiometric phosphorylation of skeletal troponin I (endogenous phosphate content 0.7 mol/mol) indicated that the Ca2+-dependent enzyme and cyclic AMP-dependent protein kinase incorporated 0.9 and 0.8 mol/mol respectively. The same experiments with skeletal troponin T (endogenous phosphate content 1.9 mol/mol) revealed a maximal phosphorylation of 2 mol/mol by the Ca2+-dependent enzyme, whereas the cyclic AMP-dependent enzyme was unable to phosphorylate troponin T. The Ca2+-dependent enzyme phosphorylated both serine and threonine residues in skeletal and cardiac troponin I or troponin T; the cyclic AMP-dependent enzyme, in comparison, phosphorylated only serine in skeletal and cardiac troponin I. Although an equimolar amount of skeletal or cardiac troponin C markedly inhibited (80-90%) phosphorylation of skeletal and cardiac troponin I by the Ca2+-dependent enzyme, these troponin C preparations inhibited only phosphorylation of skeletal troponin I, but not that of cardiac troponin I, by the cyclic AMP-dependent enzyme. Calmodulin and Ca2+-binding protein S-100a could mimic the inhibitory effect of troponin C. A tissue specificity appeared to exist for the skeletal troponin T-skeletal troponin C interaction. Inhibition of troponin T phosphorylation by an equimolar amount of troponin C was lower than that of troponin I phosphorylation; these findings might explain in part why troponin T was the major substrate for the Ca2+-dependent enzyme in the troponin complex. The present studies indicate that skeletal and cardiac troponin I and troponin T were effective substrates for phospholipid-sensitive Ca2+-dependent protein kinase, suggesting a potential involvement of this Ca2+-effector enzyme in the regulation of myofibrillar activity.

Myosin light chain kinase and cyclic AMP-dependent protein kinase activities and calmodulin levels in placental and non-placental regions of the rabbit myometrium

1986 ◽  
Vol 109 (1) ◽  
pp. 97-100 ◽  
Author(s):  
K. Matsui ◽  
K. Higashi ◽  
T. Yoshimura ◽  
M. Ito ◽  
E. Miyamoto
Keyword(s):  
Protein Kinase ◽  
Cyclic Amp ◽  
Protein Phosphorylation ◽  
Light Chain ◽  
Myosin Light Chain Kinase ◽  
Myosin Light Chain ◽  
Kinase Activity ◽  
Dependent Protein Kinase ◽  
Uterine Contractions ◽  
Dependent Protein

ABSTRACT Myosin light chain kinase activity in the placental region of the rabbit myometrium on day 28 of gestation was 4·7±0·1 (mean ± s.e.m.) nmol/min per mg protein, which was significantly higher than that (3·6 ± 0·1 nmol/min per mg protein) in the non-placental region. The amount of calmodulin in the placental region was 4·2 ± 0·1 μg/mg protein, which was significantly higher than that (3·2 ± 0·1 μg/mg protein) in the non-placental region. In contrast, cyclic AMP-dependent protein kinase activities showed no difference between the two regions. These findings suggest that calcium- and calmodulin-dependent protein phosphorylation is activated mainly in the placental region, and uterine contractions can occur more strongly in this part than in the non-placental region. Such enzymatic phenomena may be related to the mechanism whereby the placenta separates from the myometrium after delivery of the fetus. J. Endocr. (1986) 109, 97–100

scholarly journals The sites of phosphorylation of rabbit cardiac troponin I by adenosine 3′:5′-cyclic monophosphate-dependent protein kinase. Effect of interaction with troponin C

1977 ◽  
Vol 167 (2) ◽  
pp. 333-343 ◽  
Author(s):  
A J G Moir ◽  
S V Perry
Keyword(s):  
Protein Kinase ◽  
Cyclic Amp ◽  
Affinity Chromatography ◽  
Cardiac Troponin ◽  
Troponin I ◽  
Troponin C ◽  
Cardiac Troponin I ◽  
Dependent Protein Kinase ◽  
Cyclic Monophosphate ◽  
Dependent Protein

1. Troponin I prepared from rabbit hearts contains 1.0-1.5 mol of P/mol when isolated by affinity chromatography. Most of the covalently bound phosphate is located in residues 1-48 of the molecule. 2. 3′:5′-Cyclic AMP-dependent protein kinase catalyses phosphorylation at serine-20 and serine-146. Serine-20 is more rapidly phosphorylated than serine-146. 3. In troponin I prepared from frozen hearts by affinity chromatography about 0.3-0.5 mol of P/mol is associated with serine-20 and 0.8-1.0 mol of P/mol with other site(s) in residues 1-48 of the molecule. 4. Phosphorylation at serine-20 and servine-146 is not significantly inhibited by troponin C. 5. The mechansim of the interaction of troponin C with cardiac troponin I is discussed in the light of these results.

scholarly journals The phosphorylation of troponin I from cardiac muscle

1975 ◽  
Vol 149 (3) ◽  
pp. 525-533 ◽  
Author(s):  
H A Cole ◽  
S V Perry
Keyword(s):  
Skeletal Muscle ◽  
Protein Kinase ◽  
Cyclic Amp ◽  
Cardiac Muscle ◽  
Cardiac Troponin ◽  
Troponin I ◽  
Cardiac Troponin I ◽  
Phosphorylase Kinase ◽  
Dependent Protein Kinase ◽  
Dependent Protein

1. Troponin I isolated from fresh cardiac muscle by affinity chromatography contains about 1.9 mol of covalently bound phosphate/mol. Similar preparations of white-skeletal-muscle troponin I contain about 0.5 mol of phosphate/mol. 2. A 3':5'-cyclic AMP-dependent protein kinase and a protein phosphatase are associated with troponin isolated from cardiac muscle. 3. Bovine cardiac 3':5'-cyclic AMP-dependent protein kinase catalyses the phosphorylation of cardiac troponin I 30 times faster than white-skeletal-muscle troponin I. 4. Troponin I is the only component of cardiac troponin phosphorylated at a significant rate by the endogenous or a bovine cardiac 3':5'-cyclic AMP-dependent protein kinase. 5. Phosphorylase kinase catalyses the phosphorylation of cardiac troponin I at similar or slightly faster rates than white-skeletal-muscle troponin I. 6. Troponin C inhibits the phosphorylation of cardiac and skeletal troponin I catalysed by phosphorylase kinase and the phosphorylation of white skeletal troponin I catalysed by 3':5'-cyclic AMP-dependent protein kinase; the phosphorylation of cardiac troponin I catalysed by the latter enzyme is not inhibited.

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