PSI Structural Biology Knowledgebase

PSI | Structural Biology Knowledgebase
Header Icons

Related Articles
Protein Folding and Misfolding: It's the Journey, Not the Destination
March 2015
CCR5 and HIV Infection
January 2015
HIV/AIDS: Pre-fusion Env Exposed
January 2015
HIV/AIDS: Slide to Enter
January 2015
Updating ModBase
January 2015
Power in Numbers
August 2014
Quorum Sensing: A Groovy New Component
August 2014
Bacterial CDI Toxins
June 2014
Immunity: One Antibody to Rule Them All
June 2014
Virology: A Bat Influenza Hemagglutinin
March 2014
Virology: Making Sensitive Magic
March 2014
Virology: Visualizing Cyanophage Assembly
March 2014
Virology: Zeroing in on HBV Egress
March 2014
March 2014
Cas4 Nuclease and Bacterial Immunity
February 2014
Microbial Pathogenesis: A GNAT from Pseudomonas
February 2014
Microbial Pathogenesis: Targeting Drug Resistance in Mycobacterium tuberculosis
February 2014
Microbiome: The Dynamics of Infection
September 2013
Membrane Proteome: A Funnel-like Viroporin
August 2013
Infectious Diseases: A Pathogen Ubiquitin Ligase
May 2013
Infectious Diseases: A Shared Syringe
May 2013
Infectious Diseases: Determining the Essential Structome
May 2013
Infectious Diseases: Targeting Meningitis
May 2013
NDM-1 and Antibiotics
May 2013
Bacterial Hemophores
January 2013
Microbial Pathogenesis: Computational Epitope Prediction
January 2013
Microbial Pathogenesis: Influenza Inhibitor Screen
January 2013
Microbial Pathogenesis: Measles Virus Attachment
January 2013
Microbial Pathogenesis: NEAT Iron
January 2013
Membrane Proteome: Sphingolipid Synthesis Selectivity
December 2012
A signal sensing switch
September 2012
Gauging needle structure
July 2012
Anthrax Stealth Siderophores
June 2012
A Pseudomonas L-serine dehydrogenase
May 2012
Pilus Assembly Protein TadZ
April 2012
Making Lipopolysaccharide
January 2012
Superbugs and Antibiotic Resistance
December 2011
A change to resistance
November 2011
An effective and cooperative dimer
November 2011
The Perils of Protein Secretion
November 2011
Bacterial Armor
October 2011
Breaking down the defenses
September 2011
Moving some metal
August 2011
Capsid assembly in motion
April 2011
Know thy enemy … structurally
October 2010
Treating sleeping sickness
May 2010
Bacterial spore kinase
April 2010
Hemolysin BL
January 2010
Unusual cell division
October 2009
Anthrax evasion tactics
September 2009
Toxin-antitoxin VapBC-5
September 2009
Antibiotic target
August 2009
July 2009
Tackling influenza
June 2009
You look familiar: the Type VI secretion system
June 2009
Unique SARS
April 2009
Anthrax stealth molecule
March 2009
A new class of bacterial E3 ubiquitination enzymes
January 2009
Antiviral evasion
October 2008
SARS connections
September 2008
SARS Coronavirus Nonstructural Protein 1
June 2008

Research Themes Infectious diseases

Microbial Pathogenesis: A GNAT from Pseudomonas

SBKB [doi:10.1038/sbkb.2012.183]
Featured Article - February 2014
Short description: A multidisciplinary approach offers a detailed view of a bacterial acetyltransferase.

Structure of PA4794 in complex with reaction products CoA and Nε-acetylated NPAcGK peptide. (PDB: 4L8A) Interaction of the C-terminal carboxyl group of the peptide with Arg49 of PA4794 is visible. Figure courtesy of Wladek Minor.

Gnc5-related N-acetyltransferases (GNATs) are a superfamily of enzymes that transfer an acetyl group from acetyl-coenzyme A (CoA) to a wide range of substrates, including proteins and small molecules such as antibiotics and spermine. In proteins, GNATs have been found to modify the N-terminus (Nα) or internal lysine residues (Nε).

In contrast to eukaryotic GNATs, the functions of bacterial GNATs have not been well studied. Minor and colleagues (PSI MCSG and CSGID) now present a comprehensive characterization of PA4794, an enzyme from Gram-negative bacterium Pseudomonas aeruginosa, using a combination of biochemical, biophysical and crystallographic approaches.

PA4794 was initially crystallized in its apo form, as well as in complex with acetyl-CoA and CoA, which confirmed its similarities to other GNATs and revealed conformational changes that take place upon CoA binding. The authors next sought to identify the substrates for PA4794's acetyltransferase activity. A biochemical screen showed that the enzyme could acetylate L-lysine and derivatives such as Nα-Ac-L-lysine, but not Nε-acetyl lysine.

The data revealed a strong preference for the peptide N-phenylacetyl-Gly-Lys (NPAcGK), so the authors soaked crystals of apo-PA4794 with acetyl-CoA and the peptide. The structure showed the products of the reaction, namely CoA and the peptide acetylated at lysine's Nε. Here, the authors observed that the C-terminal carboxyl group of the peptide was stabilized by multiple interactions. By testing the enzyme with different peptides, they found that a free carboxyl group on Lys is important for enzymatic activity.

Finally, the catalytic mechanism of PA4794 was investigated in detail by mutagenesis and kinetic studies. The authors also identified several small molecules with inhibitory activity on PA4794, including cephalosporins. Enzymatic, isothermal calorimetry and crystallographic analyses revealed that the cephalosporin compounds act as competitive inhibitors and mimic the conformation of the acetylated peptide product.

These findings indicate that PA4794 is an acetyl transferase specific for peptides with C-terminal lysine, an activity that had not been described previously, though the identity of biological substrates of PA4797 remains to be determined. P. aeruginosa is an opportunistic pathogen that causes nosocomial infections notoriously difficult to treat, due to the bacterium's low susceptibility to antibiotics. Thus, the finding that PA4794 is inhibited by cephalosporins may have important clinical implications.

Inês Chen


  1. K.A. Majorek et al. Structural, functional and inhibition studies of a GNAT superfamily protein PA4794: a new C-terminal lysine protein acetyltransferase from Pseudomonas aeruginosa.
    J Biol Chem. 288, 30223-35 (2013). doi:10.1074/jbc.M113.501353

Structural Biology Knowledgebase ISSN: 1758-1338
Funded by a grant from the National Institute of General Medical Sciences of the National Institutes of Health