Evf, a virulence factor produced by the Drosophila pathogen Erwinia carotovora, is an S-palmitoylated protein with a new fold that binds to lipid vesicles.
Erwinia carotovora are phytopathogenic Gram-negative bacteria of agronomic interest as these bacteria are responsible for fruit soft rot and use insects as dissemination vectors. The Erwinia carotovora carotovora strain 15 (Ecc15) is capable of persisting in the Drosophila gut by the sole action of one protein, Erwinia virulence factor (Evf). However, the precise function of Evf is elusive, and its sequence does not provide any indication as to its biochemical function. We have solved the 2.0-angstroms crystal structure of Evf and found a protein with a complex topology and a novel fold. The structure of Evf confirms that Evf is unlike any virulence factors known to date. Most remarkably, we identified palmitoic acid covalently bound to the totally conserved Cys209, which provides important clues as to the function of Evf. Mutation of the palmitoic binding cysteine leads to a loss of virulence, proving that palmitoylation is at the heart of Evf infectivity and may be a membrane anchoring signal. Fluorescence studies of the sole tryptophan residue (Trp94) demonstrated that Evf was indeed able to bind to model membranes containing negatively charged phospholipids and to promote their aggregation.
Quevillon-Cheruel
Sophie
S
Institut de Biochimie et de Biophysique Moléculaire et Cellulaire, Université Paris-Sud, UMR8619-CNRS, IFR115, F-91405 Orsay, France.
Leulliot
Nicolas
N
Muniz
Carlos Acosta
CA
Vincent
Michel
M
Gallay
Jacques
J
Argentini
Manuela
M
Cornu
David
D
Boccard
Frédéric
F
Lemaître
Bruno
B
van Tilbeurgh
Herman
H
D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004330:Drosophila / Q000382:microbiology; D008563:Membrane Lipids / Q000737:chemistry* / Q000378:metabolism; D009154:Mutation; D016973:Pectobacterium carotovorum / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity; D011485:Protein Binding / Q000235:genetics; D037521:Virulence Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
D001426:Bacterial Proteins; D008563:Membrane Lipids; D037521:Virulence Factors; D003545:Cysteine