1ZUN: Crystal Structure Of A Gtp-Regulated Atp Sulfurylase Heterodimer From Pseudomonas Syringae

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.
PDB ID: 1ZUNDownload
MMDB ID: 37014
PDB Deposition Date: 2005/5/31
Updated in MMDB: 2012/11
Experimental Method:
x-ray diffraction
Resolution: 2.7  Å
Source Organism:
Pseudomonas syringae pv. tomato str. DC3000
Similar Structures:
Biological Unit for 1ZUN: dimeric; determined by author and by software (PISA)
Molecular Components in 1ZUN
Label Count Molecule
Proteins (2 molecules)
Sulfate Adenylyltransferase Subunit 2(Gene symbol: cysD)
Molecule annotation
Sulfate Adenylate Transferase, Subunit 1/adenylylsulfate Kinase(Gene symbol: cysN/C)
Molecule annotation
Chemicals (4 molecules)
* Click molecule labels to explore molecular sequence information.

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