Crystal structure of the peptidase domain of Streptococcus ComA, a bifunctional ATP-binding cassette transporter involved in the 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.
Ishii
Seiji
S
Department of Biochemistry, Osaka Medical College, Takatsuki, Osaka 569-8686, Japan.
Yano
Takato
T
Ebihara
Akio
A
Okamoto
Akihiro
A
Manzoku
Miho
M
Hayashi
Hideyuki
H
D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009154:Mutation / Q000235:genetics; D010447:Peptide Hydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D053038:Quorum Sensing; D015398:Signal Transduction; D013291:Streptococcus / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D013379:Substrate Specificity
D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; C423628:competence factor, Streptococcus; D010447:Peptide Hydrolases