1FCJ: CRYSTAL STRUCTURE OF OASS COMPLEXED WITH CHLORIDE AND SULFATE

Citation:
Abstract
A new crystal structure of O-acetylserine sulfhydrylase (OASS) has been solved with chloride bound at an allosteric site and sulfate bound at the active site. The bound anions result in a new "inhibited" conformation, that differs from the "open" native or "closed" external aldimine conformations. The allosteric site is located at the OASS dimer interface. The new inhibited structure involves a change in the position of the "moveable domain" (residues 87-131) to a location that differs from that in the open or closed forms. Formation of the external aldimine with substrate is stabilized by interaction of the alpha-carboxyl group of the substrate with a substrate-binding loop that is part of the moveable domain. The inhibited conformation prevents the substrate-binding loop from interacting with the alpha-carboxyl group, and hinders formation of the external Schiff base and thus subsequent chemistry. Chloride may be an analog of sulfide, the physiological inhibitor. Finally, these results suggest that OASS represents a new class of PLP-dependent enzymes that is regulated by small anions.
PDB ID: 1FCJDownload
MMDB ID: 14850
PDB Deposition Date: 2000/7/18
Updated in MMDB: 2000/12
Experimental Method:
x-ray diffraction
Resolution: 2  Å
Source Organism:
Similar Structures:
Biological Unit for 1FCJ: dimeric; determined by author and by software (PISA)
Molecular Components in 1FCJ
Label Count Molecule
Proteins (2 molecules)
2
O-acetylserine Sulfhydrylase(Gene symbol: cysK)
Molecule annotation
Chemicals (6 molecules)
1
2
2
2
3
2
* Click molecule labels to explore molecular sequence information.

Citing MMDB
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