The Crystal Structure of Human PAPS Synthetase 1 Reveals Asymmetry in Substrate Binding

• Published in: Journal of molecular biology Vol. 347; no. 3; pp. 623 - 635
• Main Authors: Harjes, Stefan, Bayer, Peter, Scheidig, Axel J.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.04.2005
• Subjects: Adenosine Diphosphate - metabolism; adenosine phosphosulfate; Amino Acid Sequence; asymmetric homodimer; Binding Sites; Coenzymes - metabolism; Crystallography, X-Ray; Humans; Models, Molecular; Molecular Sequence Data; Molecular Structure; Multienzyme Complexes - chemistry; Multienzyme Complexes - metabolism; P-loop; phosphoadenosine phosphosulfate; Protein Binding; Protein Structure, Tertiary; Sequence Alignment; Sulfate Adenylyltransferase - chemistry; Sulfate Adenylyltransferase - metabolism; P-loop; PAPS; APS; asymmetric homodimer; adenosine phosphosulfate; GST; phosphoadenosine phosphosulfate
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1016/j.jmb.2005.01.005

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 Å 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.