Solution structure of Ca2+-free rat alpha-parvalbumin

Protein Sci. 2008 Mar;17(3):431-8. doi: 10.1110/ps.073318308. Epub 2008 Jan 24.


Mammals express two parvalbumins-an alpha isoform and a beta isoform. In rat, the alpha-parvalbumin (alpha-PV) exhibits superior divalent ion affinity. For example, the standard free energies for Ca2+ binding differ by 5.5 kcal/mol in 0.15 M KCl (pH 7.4). High-resolution structures of the Ca2+-bound proteins provide little insight into this disparity, prompting a structural analysis of the apo-proteins. A recent analysis of rat beta-PV suggested that Ca2+ removal provokes substantial conformational changes-reorientation of the C, D, and E helices; reorganization of the hydrophobic core; reduced interdomain contact; and remodeling of the AB domain. The energetic penalty attendant to reversing these changes, it was suggested, could contribute to the attenuated divalent ion-binding signature of that protein. That hypothesis is supported by data presented herein, describing the solution structure and peptide backbone dynamics of Ca2+-free rat alpha-PV. In marked contrast to rat beta-PV, the apo- and Ca2+-loaded forms of the rat alpha isoform are quite similar. Significant structural differences appear to be confined to the loop regions of the molecule. This finding implies that the alpha-PV isoform enjoys elevated divalent ion affinity because the metal ion-binding events do not require major structural rearrangement and the concomitant sacrifice of binding energy.

Publication types

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

MeSH terms

  • Animals
  • Calcium / chemistry
  • Models, Molecular*
  • Motion
  • Nuclear Magnetic Resonance, Biomolecular
  • Parvalbumins / chemistry*
  • Rats
  • Solutions


  • Parvalbumins
  • Solutions
  • Calcium

Associated data

  • PDB/2JWW