Temperature dependence of domain motions of calmodulin probed by NMR relaxation at multiple fields.
Interdomain motions of Ca(2+)-ligated calmodulin were characterized by analyzing the nuclear magnetic resonance (15)N longitudinal relaxation rate R(1), transverse relaxation rate R(2), and steady-state {(1)H}-(15)N NOE of the backbone amide group at three different magnetic field strengths (18.8, 14.1, and 8.5 T) and four different temperatures (21, 27, 35, and 43 degrees C). Between 35 and 43 degrees C, a larger than expected change in the amplitude and the time scale of the interdomain motion for both N- and C-domains was observed. We attribute this to the shift in population of four residues (74-77) in the central linker from predominantly helical to random coil in this temperature range. This is consistent with the conformation of these residues in the calmodulin-peptide complex, where they are nonhelical. The doubling of the disordered region of the central helix (residues 78-81 at room temperature) when temperature is raised from 35 to 43 degrees C results in larger amplitude interdomain motion. Our analysis of the NMR relaxation data quantifies subtle changes in the interdomain dynamics and provides an additional tool to monitor conformational changes in multidomain proteins.
Chang
Shou-Lin
SL
Laboratory of Biophysical Chemistry, Building 50, National Heart, Lung, and Blood Institute and Laboratory of Chemical Physics, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
Szabo
Attila
A
Tjandra
Nico
N
D000818:Animals; D002147:Calmodulin / Q000737:chemistry* / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D009068:Movement; D017434:Protein Structure, Tertiary; D013696:Temperature; D014981:Xenopus
D002147:Calmodulin