2NVA: The X-ray Crystal Structure Of The Paramecium Bursaria Chlorella Virus Arginine Decarboxylase Bound To Agmatine

The group IV pyridoxal-5'-phosphate (PLP)-dependent decarboxylases belong to the beta/alpha barrel structural family, and include enzymes with substrate specificity for a range of basic amino acids. A unique homolog of this family, the Paramecium bursaria Chlorella virus arginine decarboxylase (cvADC), shares about 40% amino acid sequence identity with the eukaryotic ornithine decarboxylases (ODCs). The X-ray structure of cvADC has been solved to 1.95 and 1.8 A resolution for the free and agmatine (product)-bound enzymes. The global structural differences between cvADC and eukaryotic ODC are minimal (rmsd of 1.2-1.4 A); however, the active site has significant structural rearrangements. The key "specificity element," is identified as the 310-helix that contains and positions substrate-binding residues such as E296 cvADC (D332 in T. brucei ODC). In comparison to the ODC structures, the 310-helix in cvADC is shifted over 2 A away from the PLP cofactor, thus accommodating the larger arginine substrate. Within the context of this conserved fold, the protein is designed to be flexible in the positioning and amino acid sequence of the 310-helix, providing a mechanism to evolve different substrate preferences within the family without large structural rearrangements. Also, in the structure, the "K148-loop" (homologous to the "K169-loop" of ODC) is observed in a closed, substrate-bound conformation for the first time. Apparently the K148 loop is a mobile loop, analogous to those observed in triose phosphate isomerase and tryptophan synthetase. In conjunction with prior structural studies these data predict that this loop adopts different conformations throughout the catalytic cycle, and that loop movement may be kinetically linked to the rate-limiting step of product release.
PDB ID: 2NVADownload
MMDB ID: 45154
PDB Deposition Date: 2006/11/11
Updated in MMDB: 2017/10
Experimental Method:
x-ray diffraction
Resolution: 1.8  Å
Source Organism:
Similar Structures:
Biological Unit for 2NVA: dimeric; determined by author and by software (PISA)
Molecular Components in 2NVA
Label Count Molecule
Proteins (2 molecules)
Arginine Decarboxylase, A207r Protein
Molecule annotation
Chemicals (2 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB