The influence of trout cardiac troponin I and PKA phosphorylation on the Ca2+ affinity of the cardiac troponin complex
| Autor: | Kelly P. Kirkpatrick, Todd E. Gillis, Andrew S. Robertson, Jordan M. Klaiman |
|---|---|
| Rok vydání: | 2011 |
| Předmět: |
endocrine system
DNA Complementary Physiology animal diseases Molecular Sequence Data Protein domain Mutant macromolecular substances Aquatic Science Biology Cardiac Troponin complex chemistry.chemical_compound Troponin T Troponin I Animals Humans Myocytes Cardiac Amino Acid Sequence Phosphorylation Protein kinase A Molecular Biology Ecology Evolution Behavior and Systematics Myocardium musculoskeletal system biology.organism_classification Cyclic AMP-Dependent Protein Kinases Protein Structure Tertiary Rats Actin Cytoskeleton Trout chemistry Biochemistry Oncorhynchus mykiss Insect Science cardiovascular system Iodoacetamide Calcium Animal Science and Zoology Troponin C |
| Zdroj: | Journal of Experimental Biology. 214:1981-1988 |
| ISSN: | 1477-9145 0022-0949 |
| Popis: | SUMMARY The trout heart is 10-fold more sensitive to Ca2+ than the mammalian heart. This difference is due, in part, to cardiac troponin C (cTnC) from trout having a greater Ca2+ affinity than human cTnC. To determine what other proteins are involved, we cloned cardiac troponin I (cTnI) from the trout heart and determined how it alters the Ca2+ affinity of a cTn complex containing all mammalian components (mammalian cTn). Ca2+ activation of the complex was characterized using a human cTnC mutant that contains anilinonapthalenesulfote iodoacetamide attached to Cys53. When the cTn complex containing labeled human cTnC was titrated with Ca2+, its fluorescence changed, reaching an asymptote upon saturation. Our results reveal that trout cTnI lacks the N-terminal extension found in cTnI from all other vertebrate groups. This protein domain contains two targets (Ser23 and Ser24) for protein kinase A (PKA) and protein kinase C. When these are phosphorylated, the rate of cardiomyocyte relaxation increases. When rat cTnI in the mammalian cTn complex was replaced with trout cTnI, the Ca2+ affinity was increased ∼1.8-fold. This suggests that trout cTnI contributes to the high Ca2+ sensitivity of the trout heart. Treatment of the two cTn complexes with PKA decreased the Ca2+ affinity of both complexes. However, the change for the complex containing rat cTnI was 2.2-fold that of the complex containing trout cTnI. This suggests that the phosphorylation of trout cTnI does not play as significant a role in regulating cTn function in trout. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|