Collagen-like proteins in pathogenic E. coli strains.
The genome sequences of enterohaemorrhagic E. coli O157:H7 strains show multiple open-reading frames with collagen-like sequences that are absent from the common laboratory strain K-12. These putative collagens are included in prophages embedded in O157:H7 genomes. These prophages carry numerous genes related to strain virulence and have been shown to be inducible and capable of disseminating virulence factors by horizontal gene transfer. We have cloned two collagen-like proteins from E. coli O157:H7 into a laboratory strain and analysed the structure and conformation of the recombinant proteins and several of their constituting domains by a variety of spectroscopic, biophysical, and electron microscopy techniques. We show that these molecules exhibit many of the characteristics of vertebrate collagens, including trimer formation and the presence of a collagen triple helical domain. They also contain a C-terminal trimerization domain, and a trimeric α-helical coiled-coil domain with an unusual amino acid sequence almost completely lacking leucine, valine or isoleucine residues. Intriguingly, these molecules show high thermal stability, with the collagen domain being more stable than those of vertebrate fibrillar collagens, which are much longer and post-translationally modified. Under the electron microscope, collagen-like proteins from E. coli O157:H7 show a dumbbell shape, with two globular domains joined by a hinged stalk. This morphology is consistent with their likely role as trimeric phage side-tail proteins that participate in the attachment of phage particles to E. coli target cells, either directly or through assembly with other phage tail proteins. Thus, collagen-like proteins in enterohaemorrhagic E. coli genomes may have a direct role in the dissemination of virulence-related genes through infection of harmless strains by induced bacteriophages.
Manchester Interdisciplinary Biocentre, University of Manchester, Manchester, United Kingdom.
Neelanjana
N
Ghosh
Thomas J
TJ
McKillop
Thomas A
TA
Jowitt
Marjorie
M
Howard
H
H
Davies-Strickleton
David F
DF
Holmes
Ian S
IS
Roberts
Jordi
J
Bella
D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D003094:Collagen / Q000235:genetics / Q000378:metabolism*; D019453:Escherichia coli O157 / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D039002:Prophages / Q000235:genetics*; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry* / Q000648:ultrastructure; D017422:Sequence Analysis, DNA; D022603:Shiga Toxins / Q000235:genetics; D013045:Species Specificity; D014461:Ultracentrifugation; D014774:Virulence
D011994:Recombinant Proteins; D022603:Shiga Toxins; D003094:Collagen