Manganese (II) electron spin resonance and cadmium-113 nuclear magnetic resonance evidence for the nature of the calcium binding site in alpha-lactalbumins.
Bovine and goat alpha-lactalbumins were substituted with 113Cd(II) or Mn(II) at the strong calcium site [Murakami, K., Andree, P.J., & Berliner, L.J. (1982) Biochemistry 21, 5488-5494] and studied by 113 Cd NMR and electron spin resonance. The 113Cd chemical shifts were in the -80 to -85 ppm range vs. Cd(ClO4)2, which was almost identical with that found for several nearly octahedral (oxygen-coordinated) calcium binding proteins such as calmodulin, parvalbumin, and troponin C. The electron spin resonance spectra of bound Mn(II)-alpha-lactalbumin complexes at 9 or 35 GHz were also confirmatory of a highly symmetric (cubic) environment around the Mn(II) with only slight distortions. The near identity of this site in alpha-lactalbumin to those of calcium binding proteins containing an "EF hand domain" was remarkable despite the absence of such a domain sequence in the alpha-lactalbumin structure.
D000818:Animals; D001665:Binding Sites; D002104:Cadmium; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002417:Cattle; D004578:Electron Spin Resonance Spectroscopy; D007554:Isotopes; D007768:Lactalbumin / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008345:Manganese
D002135:Calcium-Binding Proteins; D007554:Isotopes; D002104:Cadmium; D008345:Manganese; D007768:Lactalbumin; D002118:Calcium