Troponin-tropomyosin interactions. Fluorescence studies of the binding of troponin, troponin T, and chymotryptic troponin T fragments to specifically labeled tropomyosin.
We have studied the interaction between troponin and tropomyosin by means of a fluorescent probe, N-(1- anilinonaphth -4-yl)maleimide (ANM), attached to the cysteine-190 residues of tropomyosin. The binding of troponin and troponin T to ANM-tropomyosin produces substantial increases in the label fluorescence. Analysis of the binding profiles indicates that both troponin and troponin T bind with a 1:1 stoichiometry. We have obtained and characterized several chymotryptic fragments of troponin T by digestion of isolated troponin T or whole troponin. An N-terminal fragment from troponin T which is slightly less than two-thirds of the whole molecule binds to tropomyosin without affecting the label fluorescence; a C-terminal fragment composed of the rest of the troponin T molecule causes a substantial enhancement of the label fluorescence. We have also isolated a complex containing the C-terminal troponin T fragment together with troponin I and troponin C from whole troponin, which also enhanced the label fluorescence. These observations indicate an elongated region of attachment between troponin T and tropomyosin.
D000595:Amino Acid Sequence; D000818:Animals; D002918:Chymotrypsin / Q000378:metabolism; D007202:Indicators and Reagents / Q000378:metabolism; D008301:Maleimides / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism; D011817:Rabbits; D013050:Spectrometry, Fluorescence; D014335:Tropomyosin / Q000378:metabolism*; D014336:Troponin / Q000378:metabolism*; D020107:Troponin T
D007202:Indicators and Reagents; D008301:Maleimides; D010446:Peptide Fragments; D014335:Tropomyosin; D014336:Troponin; D020107:Troponin T; C010854:N-(1-anilinonaphthalyl)-4-maleimide; D002918:Chymotrypsin