Antigen/Purification: Collapse
The antigen is a fusion protein of the mouse cardiac troponin I holoprotein.
The antibody is unpurified neat serum.
Biological Significance: Collapse
Troponin I (cTnI) is 1 of 3 subunits, along with troponin C (TnC) and troponin T (TnT) of troponin complex found in cardiac muscle. cTnI binds to actin in thin myofilaments to hold the troponin-tropomyosin complex in place. Phosphorylation of cardiac isoform of TnI at serines 22,23 in the unique amino-terminal end molecule decreases the calcium sensitivity of the sarcomere, promotes calcium dissociation from troponin C and by extension enhances rates of cross-bridge cycling and diastolic relaxation (Noland, Jr. et al., 1995; Noland et al., 1989). In addition, studies using reconstituted fibers and mutational analysis have shown that PKC phosphorylation of TnI (largely at Ser43) inhibits the actin-cross bridge reaction and reduces the Ca++ dependent actomyosin ATPase rate as well as the calcium sensitivity of force generation (Noland, Jr. and Kuo, 1991). Phosphorylation at Thr144 (mediated by several PKC isoforms) reduces maximal tension development and cross-bridge cycling rates (Sumandea et al., 2008). Importantly, changes in the phosphorylation at each of these sites have been shown to be stage-specific with regard to cardiac disease progression (Walker et al., 2010).
Storage
100 μl neat serum. Adequate amount of material to conduct 10-mini Western blots.
For long term storage –20° C is recommended. Stable at –20° C for at least 1 year.
General References
Noland TA, Jr., Guo XD, Raynor RL, Jideama NM, Averyhart-Fullard V, Solaro RJ, Kuo JF (1995) Cardiac troponin I mutants – Phosphorylation by protein kinases C and A and regulation of Ca2+-stimulated MgATPase of reconstituted actomyosin S-1. J Biol Chem 270: 25445-25454.
Noland TA, Jr., Kuo JF (1991) Protein kinase C phosphorylation of cardiac troponin I or troponin T inhibits Ca2(+)-stimulated actomyosin MgATPase activity. J Biol Chem 266: 4974-4978.
Noland TAJr, Raynor RL, Kuo JF (1989) Identification of sites phosphorylated in bovine cardiac troponin I and troponin T by protein kinase C and comparative substrate activity of synthetic peptides containing the phosphorylation sites. J Biol Chem 264: 20778-20785.
Sumandea MP, Rybin VO, Hinken AC, Wang C, Kobayashi T, Harleton E, Sievert G, Balke CW, Feinmark SJ, Solaro RJ, Steinberg SF (2008) Tyrosine phosphorylation modifies protein kinase C delta-dependent phosphorylation of cardiac troponin I. J Biol Chem 283: 22680-22689.
Walker LA, Walker JS, Ambler SK, Buttrick PM (2010) Stage-specific changes in myofilament protein phosphorylation following myocardial infarction in mice. J Mol Cell Cardiol 48: 1180-1186
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