Spin labeling studies of wheat germ calmodulin in solution

Mary Anne Yacko, Thomas C. Vanaman, D. Allan Butterfield

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Electron paramagnetic resonance was used to investigate the physical state of plant calmodulin in solution. Wheat germ calmodulin contains a single cysteine residue (Cys-27) on the first of four calcium binding loops. In this study the nitroxide spin label 2,2,6,6-tetramethyl-4-maleimidopiperidine-1-oxyl (MAL-6) was covalently attached to Cys-27 to produce a Ca2+-sensitive, biologically-active, labeled protein. The rotational correlation time of the spin label, a measure of its rotational mobility and reflective of the physical state of this region of the protein, was calculated under various conditions. Relative to control, changes in the physical state of the protein reflected by increased motion of the spin label were observed at high pH, low ionic strength and upon addition of Ca2+. These results extend knowledge of the structure of the protein, previously known from solid state and biochemical studies, to calmodulin in solution.

Original languageEnglish
Pages (from-to)7-12
Number of pages6
JournalBBA - Biomembranes
Issue number1
StatePublished - Apr 26 1991

Bibliographical note

Funding Information:
The authors thank Ms. Lori Dwyer for technical assistance, and Con Agra for donating the wheat germ. This work was supported in part by a NSF grant (RII-86-10671), (D.A.B.).


  • Calmodulin
  • Conformation
  • EPR
  • Spin label

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology


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