Troponin I encompasses an extended troponin C in the Ca(2+)-bound complex: a small-angle X-ray and neutron scattering study.
We have studied the solution structure of skeletal muscle troponin C complexed with troponin I in the presence of calcium using small-angle X-ray and neutron scattering. 4Ca2+.troponin C in the complex has an extended dumbbell shape with a radius of gyration of 23.9 +/- 0.5 A and a maximum linear dimension of approximately 72 A, similar to the values obtained from the crystal structure coordinates of troponin C (Herzberg & James, 1985). Troponin I is even more extended than troponin C with a radius of gyration of 41 +/- 2 A and a maximum linear dimension of approximately 118 A. The centers-of-mass for each component of the complex are approximately coincident (< 10-A separation) as are their long axes, and the troponin I component encompasses the 4Ca2+.troponin C. These data provide new insights into the nature of the conformational arrangement of this important Ca(2+)-sensitive molecular switch.
Chemical Science and Technology Division, Los Alamos National Laboratory, New Mexico 87545.
G A
GA
Olah
S E
SE
Rokop
C L
CL
Wang
S L
SL
Blechner
J
J
Trewhella
D002118:Calcium / Q000378:metabolism*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003903:Deuterium; D009132:Muscles / Q000737:chemistry*; D009502:Neutrons; D011487:Protein Conformation; D012542:Scattering, Radiation; D014336:Troponin / Q000737:chemistry* / Q000378:metabolism*; D019209:Troponin C; D019210:Troponin I; D014965:X-Rays
D014336:Troponin; D019209:Troponin C; D019210:Troponin I; D003903:Deuterium; D002118:Calcium