1I29: Crystal Structure Of Csdb Complexed With L-propargylglycine

Escherichia coli CsdB is a pyridoxal 5'-phosphate (PLP)-dependent enzyme that catalyzes both cysteine desulfuration and selenocysteine deselenation. The enzyme has a high specific activity for L-selenocysteine relative to L-cysteine. On the other hand, its paralog, IscS, exhibits higher activity for L-cysteine, which acts as a sulfur donor during the biosynthesis of the iron-sulfur cluster and 4-thiouridine. The structure of CsdB complexed with L-propargylglycine was determined by X-ray crystallography at 2.8 A resolution. The overall polypeptide fold of the complex is similar to that of the uncomplexed enzyme, indicating that no significant structural change occurs upon formation of the complex. In the complex, propargylglycine forms a Schiff base with PLP, providing the features of the external aldimine formed in the active site. The Cys364 residue, which is essential for the activity of CsdB toward L-cysteine but not toward L-selenocysteine, is clearly visible on a loop of the extended lobe (Thr362-Arg375) in all enzyme forms studied, in contrast to the corresponding disordered loop (Ser321-Arg332) of the Thermotoga maritima NifS-like protein, which is closely related to IscS. The extended lobe of CsdB has an 11-residue deletion compared with that of the NifS-like protein. These facts suggest that the restricted flexibility of the Cys364-anchoring extended lobe in CsdB may be responsible for the ability of the enzyme to discriminate between selenium and sulfur.
PDB ID: 1I29Download
MMDB ID: 23267
PDB Deposition Date: 2001/2/7
Updated in MMDB: 2012/11
Experimental Method:
x-ray diffraction
Resolution: 2.8  Å
Source Organism:
Similar Structures:
Biological Unit for 1I29: dimeric; determined by author and by software (PISA,PQS)
Molecular Components in 1I29
Label Count Molecule
Proteins (2 molecules)
Molecule annotation
Chemicals (4 molecules)
* Click molecule labels to explore molecular sequence information.

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