Crystallization and preliminary X-ray analysis of human grancalcin, a novel cytosolic Ca²⁺-binding protein present in leukocytes

Recombinant human grancalcin, a calcium-binding protein from leukocytes, has been crystallized in the presence or absence of Ca²⁺ by the vapor-diffusion method. Two crystal forms of apo grancalcin were obtained: space group P2₁, with unit-cell parameters a = 48.4, b = 81.1, c = 46.6 Å, β = 111.3°, diffracting to 1.9 Å, and space group C2, with unit-cell parameters a = 97.0, b = 51.9, c = 75.9 Å, β = 108.5°, diffracting to 2.4 Å. Crystals were also grown in the presence of 5 mM Ca²⁺. They also belong to space group C2, with unit-cell parameters a = 97.4, b = 50.3, c = 77.6 Å, β = 108.2°, which are very similar to the second apo grancalcin form. These crystals diffract to 2.5 Å.