Solution structure of the novel dispersin protein of enteroaggregative Escherichia coli.
Enteroaggregative Escherichia coli (EAEC), increasingly recognized as an important cause of infant and travelers' diarrhoea, exhibits an aggregative, stacked-brick pattern of adherence to epithelial cells. Adherence is mediated by aggregative adherence fimbriae (AAFs), which are encoded on the pAA virulence plasmid. We recently described a highly prevalent pAA plasmid-borne gene, aap, which encodes a protein (nicknamed dispersin) that is secreted to the bacterial cell surface. Dispersin-null mutants display a unique hyper-aggregating phenotype, accompanied by collapse of AAF pili onto the bacterial cell surface. To study the mechanism of this effect, we solved the structure of dispersin from EAEC strain 042 using solution NMR, revealing a stable beta-sandwich with a conserved net positive surface charge of +3 to +4 among 23 dispersin alleles. Experimental data suggest that dispersin binds non-covalently to lipopolysaccharide on the surface of the bacterium. We also show that the AAF organelles contribute positive charge to the bacterial surface, suggesting that dispersin's role in fimbrial function is to overcome electrostatic attraction between AAF and the bacterial surface.
Velarde
Jorge J
JJ
Center for Vaccine Development, Department of Pediatrics, University of Maryland School of Medicine, Baltimore, Maryland, USA. jvela001@umaryland.edu
Varney
Kristen M
KM
Inman
Keith G
KG
Farfan
Mauricio
M
Dudley
Edward
E
Fletcher
Jonathan
J
Weber
David J
DJ
Nataro
James P
JP
D004926:Escherichia coli / Q000737:chemistry*; D029968:Escherichia coli Proteins / Q000737:chemistry*; D008070:Lipopolysaccharides / Q000378:metabolism; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary
C479827:AAP protein, E coli; D029968:Escherichia coli Proteins; D008070:Lipopolysaccharides