3PC4: Full Length Structure Of Cystathionine Beta-synthase From Drosophila In Complex With Serine

The catalytic potential for H(2)S biogenesis and homocysteine clearance converge at the active site of cystathionine beta-synthase (CBS), a pyridoxal phosphate-dependent enzyme. CBS catalyzes beta-replacement reactions of either serine or cysteine by homocysteine to give cystathionine and water or H(2)S, respectively. In this study, high-resolution structures of the full-length enzyme from Drosophila in which a carbanion (1.70 A) and an aminoacrylate intermediate (1.55 A) have been captured are reported. Electrostatic stabilization of the zwitterionic carbanion intermediate is afforded by the close positioning of an active site lysine residue that is initially used for Schiff base formation in the internal aldimine and later as a general base. Additional stabilizing interactions between active site residues and the catalytic intermediates are observed. Furthermore, the structure of the regulatory "energy-sensing" CBS domains, named after this protein, suggests a mechanism for allosteric activation by S-adenosylmethionine.
PDB ID: 3PC4Download
MMDB ID: 86664
PDB Deposition Date: 2010/10/21
Updated in MMDB: 2010/12
Experimental Method:
x-ray diffraction
Resolution: 1.7  Å
Source Organism:
Similar Structures:
Biological Unit for 3PC4: dimeric; determined by author and by software (PISA)
Molecular Components in 3PC4
Label Count Molecule
Proteins (2 molecules)
Cg1753, Isoform a
Molecule annotation
Chemicals (6 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB