The crystal structure of human 3'-phosphoadenosine-5'-phosphosulfate synthetase 1
[PAPS1_HUMAN] Bifunctional enzyme with both ATP sulfurylase and APS kinase activity, which mediates two steps in the sulfate activation pathway. The first step is the transfer of a sulfate group to ATP to yield adenosine 5'-phosphosulfate (APS), and the second step is the transfer of a phosphate group from ATP to APS yielding 3'-phosphoadenylylsulfate (PAPS: activated sulfate donor used by sulfotransferase). In mammals, PAPS is the sole source of sulfate; APS appears to be only an intermediate in the sulfate-activation pathway. Also involved in the biosynthesis of sulfated L-selectin ligands in endothelial cells.
Publication Abstract from PubMed
The high energy sulfate donor 3'-phosphoadenosine-5-phosphosulfate (PAPS) is used for sulfate conjugation of extracellular matrix, hormones and drugs. Human PAPS synthetase 1 catalyzes two subsequent reactions starting from ATP and sulfate. First the ATP sulfurylase domain forms APS, then the APS kinase domain phosphorylates the APS intermediate to PAPS. Up to now the interaction between the two enzymatic activities remained elusive, mainly because of missing structural information. Here we present the crystal structure of human PAPSS1 at 1.8 angstroms resolution. The structure reveals a homodimeric, asymmetric complex with the shape of a chair. The two kinase domains adopt different conformational states, with only one being able to bind its two substrates. The asymmetric binding of ADP to the APS kinase is not only observed in the crystal structure, but can also be detected in solution, using an enzymatic assay. These observations strongly indicate structural changes during the reaction cycle. Furthermore crystals soaked with ADP and APS could be prepared and the corresponding structures could be solved.
The crystal structure of human PAPS synthetase 1 reveals asymmetry in substrate binding.,Harjes S, Bayer P, Scheidig AJ J Mol Biol. 2005 Apr 1;347(3):623-35. Epub 2005 Jan 26. PMID:15755455
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.