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Structural basis for the negative allostery between Ca 2+ ‐ and Mg 2+ ‐binding in the intracellular Ca 2+ ‐receptor calbindin D 9k
Author(s) -
Andersson Maria,
Ivarsson Ianrik,
Anders Svensson L.,
Malmendal Anders,
Linse Sara,
Forsén Sture
Publication year - 1997
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1002/pro.5560060602
Subject(s) - isotopes of calcium , chemistry , intracellular , crystallography , physics , calcium , biochemistry , organic chemistry
The three‐dimensional structures of the magnesium‐ and manganese‐bound forms of calbindin D 9% were determined to 1.6 Å and 1.9 Å resolution, respectively, using X‐ray crystallography. These two structures are nearly identical but deviate significantly from both the calcium bound form and the metal ion‐free (apo) form. The largest structural differences are seen in the C‐terminal EF‐hand, and involve changes in both metal ion coordination and helix packing. The N‐terminal calcium binding site is not occupied by any metal ion in the magnesium and manganese structures, and shows little structural deviation from the apo and calcium bound forms. 1 H‐NMR and UV spectroscopic studies at physiological ion concentrations show that the C‐terminal site of the protein is significantly populated by magnesium at resting cell calcium levels, and that there is a negative allosteric interaction between magnesium and calcium binding. Calcium binding was found to occur with positive cooperativity at physiological magnesium concentration.