In situ orientations of protein domains: Troponin C in skeletal muscle fibers

TY - JOUR

T1 - In situ orientations of protein domains: Troponin C in skeletal muscle fibers

AU - Ferguson, R E

AU - Sun, Y B

AU - Mercier, P

AU - Brack, A S

AU - Sykes, B D

AU - Corrie, J E T

AU - Trentham, D R

AU - Irving, M

PY - 2003/4/1

Y1 - 2003/4/1

N2 - A recently developed approach for mapping protein-domain orientations in the cellular environment was used to investigate the Ca2+-dependent structural changes in the tropomyosin/troponin complex on the actin filament that regulate muscle contraction. Polarized fluorescence from bifunctional rhodamine probes attached along four alpha helices of troponin C (TnC) was measured in permeabilized skeletal muscle fibers. In relaxed muscle, the N-terminal lobe of TnC is less closed than in crystal structures of the Call-free domain, and its D helix is approximately perpendicular to the actin filament. In contrast to crystal structures of isolated TnC, the D and E helices are not collinear. On muscle activation, the N lobe orientation becomes more disordered and the average angle between the C helix and the filament changes by 32degrees +/- 5degrees. These results illustrate the potential of in situ measurements of helix and domain orientations for elucidating structure-function relations in native macromolecular complexes.

AB - A recently developed approach for mapping protein-domain orientations in the cellular environment was used to investigate the Ca2+-dependent structural changes in the tropomyosin/troponin complex on the actin filament that regulate muscle contraction. Polarized fluorescence from bifunctional rhodamine probes attached along four alpha helices of troponin C (TnC) was measured in permeabilized skeletal muscle fibers. In relaxed muscle, the N-terminal lobe of TnC is less closed than in crystal structures of the Call-free domain, and its D helix is approximately perpendicular to the actin filament. In contrast to crystal structures of isolated TnC, the D and E helices are not collinear. On muscle activation, the N lobe orientation becomes more disordered and the average angle between the C helix and the filament changes by 32degrees +/- 5degrees. These results illustrate the potential of in situ measurements of helix and domain orientations for elucidating structure-function relations in native macromolecular complexes.

UR - http://www.scopus.com/inward/record.url?scp=0037961726&partnerID=8YFLogxK

U2 - 10.1016/S1097-2765(03)00096-0

DO - 10.1016/S1097-2765(03)00096-0

M3 - Article

VL - 11

SP - 865

EP - 874

JO - MOLECULAR CELL

JF - MOLECULAR CELL

IS - 4

ER -