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 x 100 x 300 micro m and diffract to 1.75 A.