title: Molecular basis for G protein control of the prokaryotic ATP sulfurylase.
abstract: Sulfate assimilation is a critical component of both primary and secondary metabolism. An essential step in this pathway is the activation of sulfate through adenylation by the enzyme ATP sulfurylase (ATPS), forming adenosine 5'-phosphosulfate (APS). Proteobacterial ATPS overcomes this energetically unfavorable reaction by associating with a regulatory G protein, coupling the energy of GTP hydrolysis to APS formation. To discover the molecular basis of this unusual role for a G protein, we biochemically characterized and solved the X-ray crystal structure of a complex between Pseudomonas syringae ATPS (CysD) and its associated regulatory G protein (CysN). The structure of CysN*D shows the two proteins in tight association; however, the nucleotides bound to each subunit are spatially segregated. We provide evidence that conserved switch motifs in the G domain of CysN allosterically mediate interactions between the nucleotide binding sites. This structure suggests a molecular mechanism by which conserved G domain architecture is used to energetically link GTP turnover to the production of an essential metabolite.
authors.affiliation: Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, California 94720, USA.
authors.forename: Joseph D
authors.initials: JD
authors.lastname: Mougous
authors.forename: Dong H
authors.initials: DH
authors.lastname: Lee
authors.forename: Sarah C
authors.initials: SC
authors.lastname: Hubbard
authors.forename: Michael W
authors.initials: MW
authors.lastname: Schelle
authors.forename: David J
authors.initials: DJ
authors.lastname: Vocadlo
authors.forename: James M
authors.initials: JM
authors.lastname: Berger
authors.forename: Carolyn R
authors.initials: CR
authors.lastname: Bertozzi
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018360:Crystallography, X-Ray; D019281:Dimerization; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D017434:Protein Structure, Tertiary; D044224:Pseudomonas syringae / Q000201:enzymology* / Q000235:genetics; D016415:Sequence Alignment; D013430:Sulfate Adenylyltransferase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013431:Sulfates / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D013431:Sulfates; D006160:Guanosine Triphosphate; D013430:Sulfate Adenylyltransferase; D019204:GTP-Binding Proteins