2CNS: RimI - Ribosomal S18 N-alpha-protein acetyltransferase in complex with acetylCoA

The three ribosomal proteins L7, S5, and S18 are included in the rare subset of prokaryotic proteins that are known to be N(alpha)-acetylated. The GCN5-related N-acetyltransferase (GNAT) protein RimI, responsible for the N(alpha)-acetylation of the ribosomal protein S18, was cloned from Salmonella typhimurium LT2 (RimI(ST)), overexpressed, and purified to homogeneity. Steady-state kinetic parameters for RimI(ST) were determined for AcCoA and a peptide substrate consisting of the first six amino acids of the target protein S18. The crystal structure of RimI(ST) was determined in complex with CoA, AcCoA, and a CoA-S-acetyl-ARYFRR bisubstrate inhibitor. The structures are consistent with a direct nucleophilic addition-elimination mechanism with Glu103 and Tyr115 acting as the catalytic base and acid, respectively. The RimI(ST)-bisubstrate complex suggests that several residues change conformation upon interacting with the N terminus of S18, including Glu103, the proposed active site base, facilitating proton exchange and catalysis.
PDB ID: 2CNSDownload
MMDB ID: 46877
PDB Deposition Date: 2006/5/23
Updated in MMDB: 2008/10
Experimental Method:
x-ray diffraction
Resolution: 2.5  Å
Source Organism:
Similar Structures:
Biological Unit for 2CNS: monomeric; determined by author and by software (PQS)
Molecular Components in 2CNS
Label Count Molecule
Protein (1 molecule)
Modification of 30S Ribosomal Subunit Protein S18
Molecule annotation
Chemicals (2 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB