2OLB: Oligopeptide Binding Protein (Oppa) Complexed With Tri- Lysine

BACKGROUND: The periplasmic oligopeptide-binding protein OppA has a remarkably broad substrate specificity, binding peptides of two or five amino-acid residues with high affinity, but little regard to sequence. It is therefore an ideal system for studying how different chemical groups can be accommodated in a protein interior. The ability of the protein to bind peptides of different lengths has been studied by co-crystallising it with different ligands. RESULTS: Crystals of OppA from Salmonella typhimurium complexed with the peptides Lys-Lys-Lys (KKK) and Lys-Lys-Lys-Ala (KKKA) have been grown in the presence of uranyl ions which form important crystal contacts. These structures have been refined to 1.4 A and 2.1 A, respectively. The ligands are completely enclosed, their side chains pointing into large hydrated cavities and making few strong interactions with the protein. CONCLUSIONS: Tight peptide binding by OppA arises from strong hydrogen bonding and electrostatic interactions between the protein and the main chain of the ligand. Different basic side chains on the protein form salt bridges with the C terminus of peptide ligands of different lengths.
PDB ID: 2OLBDownload
MMDB ID: 3840
PDB Deposition Date: 1995/9/10
Updated in MMDB: 1998/11
Experimental Method:
x-ray diffraction
Resolution: 1.4  Å
Source Organism:
Salmonella enterica subsp. enterica serovar Typhimurium
Similar Structures:
Biological Unit for 2OLB: dimeric; determined by author and by software (PISA)
Molecular Components in 2OLB
Label Count Molecule
Proteins (2 molecules)
Oligo-peptide Binding Protein(Gene symbol: oppA)
Molecule annotation
Tripeptide Lys-lys-lys
Molecule annotation
Chemicals (14 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB