Backbone dynamics of calmodulin studied by 15N relaxation using inverse detected two-dimensional NMR spectroscopy: the central helix is flexible

Biochemistry. 1992 Jun 16;31(23):5269-78. doi: 10.1021/bi00138a005.


The backbone dynamics of Ca(2+)-saturated recombinant Drosophila calmodulin has been studied by 15N longitudinal and transverse relaxation experiments, combined with 15N(1H) NOE measurements. Results indicate a high degree of mobility near the middle of the central helix of calmodulin, from residue K77 through S81, with order parameters (S2) in the 0.5-0.6 range. The anisotropy observed in the motion of the two globular calmodulin domains is much smaller than expected on the basis of hydrodynamic calculations for a rigid dumbbell type structure. This indicates that, for the purposes of 15N relaxation, the tumbling of the N-terminal (L4-K77) and C-terminal (E82-S147) lobes of calmodulin is effectively independent. A slightly shorter motional correlation time (tau c approximately 6.3 ns) is obtained for the C-terminal domain compared to the N-terminal domain (tau c approximately 7.1 ns), in agreement with the smaller size of the C-terminal domain. A high degree of mobility, with order parameters of approximately 0.5, is also observed in the loop that connects the first with the second EF-hand type calcium binding domain and in the loop connecting the third and fourth calcium binding domain.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Calmodulin / chemistry*
  • Calmodulin / ultrastructure
  • Drosophila melanogaster
  • Magnetic Resonance Spectroscopy
  • Motion
  • Protein Conformation
  • Recombinant Proteins
  • Rotation


  • Calmodulin
  • Recombinant Proteins