Cloning and Expression of the dnaK Gene of Campylobacter jejuni and Antigenicity of Heat Shock Protein 70

Abstract

ABSTRACT Campylobacter jejuni is a leading cause of infectious diarrhea throughout the world. In addition, there is growing evidence that Guillain-Barré syndrome, an inflammatory demyelinating disease of the peripheral nervous system, is frequently preceded by C. jejuni infection. In the present study, the hrcA-grpE-dnaK gene cluster of C. jejuni was cloned and sequenced. The dnaK gene consists of an open reading frame of 1,869 bp and encodes a protein with a high degree of homology to other bacterial 70-kDa heat shock proteins (HSPs). The overall percentages of identity to the HSP70 proteins of Helicobacter pylori , Borrelia burgdorferi , Chlamydia trachomatis , and Bacillus subtilis were calculated to be 78.1, 60.5, 57.2, and 53.8%, respectively. Regions similar to the Escherichia coli ς 70 promoter consensus sequence and to a cis -acting regulatory element (CIRCE) are located upstream of the hrcA gene. Following heat shock, a rapid increase of dnaK mRNA was detectable, which reached its maximum after 20 to 30 min. A 6-His-tagged recombinant DnaK protein (rCjDnaK-His) was generated in E. coli , after cloning of the dnaK coding region into pET-22b(+), and purified by affinity and gel filtration chromatography. Antibody responses to rCjDnaK-His were significantly elevated, compared to those of healthy individuals, in about one-third of the serum specimens obtained from C. jejuni enteritis patients.