3K8U: Crystal Structure Of The Peptidase Domain Of Streptococcus Coma, A Bi- Functional Abc Transporter Involved In Quorum Sensing Pathway

ComA of Streptococcus is a member of the bacteriocin-associated ATP-binding cassette transporter family and is postulated to be responsible for both the processing of the propeptide ComC and secretion of the mature quorum-sensing signal. The 150-amino acid peptidase domain (PEP) of ComA specifically recognizes an extended region of ComC that is 15 amino acids in length. It has been proposed that an amphipathic alpha-helix formed by the N-terminal leader region of ComC, as well as the Gly-Gly motif at the cleavage site, is critical for the PEP-ComC interaction. To elucidate the substrate recognition mechanism, we determined the three-dimensional crystal structure of Streptococcus mutans PEP and then constructed models for the PEP.ComC complexes. PEP had an overall structure similar to the papain-like cysteine proteases as has long been predicted. The active site was located at the bottom of a narrow cleft, which is suitable for binding the Gly-Gly motif. Together with the results from mutational experiments, a shallow hydrophobic concave surface of PEP was proposed as a site that accommodates the N-terminal helix of ComC. This dual mode of substrate recognition would provide the small PEP domain with an extremely high substrate specificity.
PDB ID: 3K8UDownload
MMDB ID: 80268
PDB Deposition Date: 2009/10/14
Updated in MMDB: 2011/05
Experimental Method:
x-ray diffraction
Resolution: 1.9  Å
Source Organism:
Similar Structures:
Biological Unit for 3K8U: monomeric; determined by author and by software (PISA)
Molecular Components in 3K8U
Label Count Molecule
Protein (1 molecule)
Putative ABC Transporter, Atp-binding Protein Coma
Molecule annotation
* Click molecule labels to explore molecular sequence information.

Citing MMDB