Purification, crystallization and preliminary X-ray diffraction analysis of the yeast Sec12Δp protein, a guanine nucleotide-exchange factor involved in vesicle transport

Sec12 is a guanine nucleotide‐exchange factor (GEF) of the GTP‐binding protein Sar1. Its GEF activity on Sar1 makes it a key element in vesicle budding from the endoplasmic reticulum to the Golgi apparatus in yeast. Sec12 is an integral membrane glycoprotein of 70 kDa. A 38.5 kDa N‐cytoplasmic domain (Sec12Δp) has been expressed in Saccharomyces cerevisiae and in Escherichia coli, purified to homogeneity and crystallized. Two crystal forms were obtained. Crystal form I belongs to space group P62/P64, with unit‐cell parameters a = b = 191.7, c = 53.3 Å, γ = 120°, and diffracts to 2.6 Å resolution. Crystal form II belongs to space group P1, with unit‐cell parameters a = 52.6, b = 53.0, c = 116.8 Å, α = 98.0, β = 97.4, γ = 93.4°, and diffracts to 2.0 Å resolution.