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Journal of Clinical Microbiology, Nov 1995, 2826-2832, Vol 33, No. 11
A Burnens, U Stucki, J Nicolet and J Frey
We cloned and expressed in Escherichia coli a gene encoding an 18-kDa outer
membrane protein (Omp18) from Campylobacter jejuni ATCC 29428. The
nucleotide sequence of the gene encoding Omp18 was determined, and an open
reading frame of 165 amino acids was revealed. The amino acid sequence had
the typical features of a leader sequence and a signal peptidase II
cleavage site at the N-terminal part of Omp18. Moreover, the sequence had a
high degree of similarity to the peptidoglycan- associated outer membrane
lipoprotein P6 of Haemophilus influenzae and the peptidoglycan-associated
lipoprotein PAL of E. coli. Southern blot analysis in which the cloned gene
was used as a probe revealed genes similar to that encoding Omp18 in all
species of the thermophilic group of campylobacters as well as
Campylobacter sputorum. All campylobacters tested expressed a protein with
a molecular mass identical to that of Omp18. The protein reacted
immunologically with polyclonal antibodies directed against Omp18 from C.
jejuni. PCR amplification of the gene encoding Omp18 with specific primers
and subsequent restriction enzyme analysis of the amplified DNA fragments
showed that the gene for Omp18 is highly conserved in C. jejuni strains
isolated from humans, dogs, cats, calves, and chickens but is different in
other Campylobacter species. In order to obtain pure recombinant Omp18
protein for serological assays, the cloned gene for Omp18 was genetically
modified by replacing the signal sequence with a DNA segment encoding six
adjacent histidine residues. Expression of this construct in E. coli
allowed purification of the modified protein (Omp18-6xHis) by metal
chelation chromatography. Sera from patients with past C. jejuni infection
reacted positively with Omp18-6xHis, while sera from healthy blood donors
showed no reaction with this antigen. Omp18, which is an outer membrane
protein belonging to the family of PALs is well conserved in C. jejuni and
is highly immunogenic. It is therefore a good candidate as an antigen for
the serological diagnosis of past C. jejuni infections.
Copyright © 1995 by the American Society for Microbiology. All rights reserved.
Identification and characterization of an immunogenic outer membrane protein of Campylobacter jejuni
Institute for Veterinary Bacteriology, University of Berne, Switzerland.
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