The crystal structure of the protein YhaK from Escherichia coli reveals a new subclass of redox sensitive enterobacterial bicupins.

Proteins

Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, 10691 Stockholm, Sweden.

Published: January 2009

AI Article Synopsis

  • YhaK is a protein found in low amounts in E. coli, shown to be up-regulated by nitroso-glutathione and during biofilm growth in human urine.
  • The protein features a unique bicupin structure with specific cysteine oxidation and chloride ions, which may indicate a role in oxidative stress response.
  • Unlike similar proteins, YhaK lacks typical metal-binding properties and does not display common enzymatic activities, suggesting a new subclass of bicupins potentially involved in oxidative stress sensing.

Article Abstract

YhaK is a protein of unknown function found in low abundance in the cytosol of Escherichia coli. DNA array studies have revealed that YhaK is strongly up-regulated by nitroso-glutathione (GSNO) and also displays a 12-fold increase in expression during biofilm growth of E. coli 83972 and VR50 in human urine. We have determined the YhaK crystal structure and demonstrated that in vitro YhaK is a good marker for monitoring oxidative stresses in E. coli. The YhaK protein structure shows a bicupin fold where the two cupin domains are crosslinked with one intramolecular disulfide bond (Cys10 to Cys204). We found that the third cysteine in YhaK, Cys122, is oxidized to a sulfenic acid. Two chloride ions are found in the structure, one close to the reactive Cys122, and the other on a hydrophobic surface close to a symmetry-related molecule. There are major structural differences at the N-terminus of YhaK compared with similar structures that also display the bicupin fold (YhhW and hPirin). YhaK showed no quercetinase and peroxidase activity. However, reduced YhaK was very sensitive to reactive oxygen species (ROS). The complete, functional E. coli glutaredoxin or thioredoxin systems protected YhaK from oxidation. E. coli thioredoxin reductase and NADPH produced ROS and caused oxidation and oligomerization of reduced YhaK. Taken together, we propose that YhaK is the first of a new sub-class of bicupins that lack the canonical cupin metal-binding residues of pirins and may be involved in chloride binding and/or sensing of oxidative stress in enterobacteria.

Download full-text PDF

Source
http://dx.doi.org/10.1002/prot.22128DOI Listing

Publication Analysis

Top Keywords

yhak
13
crystal structure
8
escherichia coli
8
yhak protein
8
bicupin fold
8
reduced yhak
8
coli
6
structure protein
4
protein yhak
4
yhak escherichia
4

Similar Publications

Want AI Summaries of new PubMed Abstracts delivered to your In-box?

Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!