Expression, purification and crystallization of human 3′-phosphoadenosine-5′-phosphosulfate synthetase 1

3′-Phosphoadenosine-5′-phosphosulfate (PAPS) is used to incorporate sulfate into biomolecules. The human PAPS synthetase 1 catalyzes two steps leading from adenosine triphosphate (ATP) and sulfate to PAPS. The ATP sulfurylase domain catalyzes the formation of the intermediate adenosine-5′-phosphosulfate (APS). The APS kinase domain then adds a phosphate group to the 3′-ribose and releases PAPS. In this article, the recombinant expression, purification and crystallization of the full-length protein is described. In Escherichia coli the protein is only partly soluble and copurifies with GroEL. The pure protein migrates as a dimer in gel-filtration chromatography. It is moderately active, forming 25 nmol PAPS per minute per milligram. Crystals grow to 100 × 100 × 300 µm and diffract to 1.75 Å.