Identification and characterization of an RTX toxin-like gene and its operon from Avibacterium paragallinarum.
Avibacterium paragallinarum is the causative agent of infectious coryza, an important respiratory disease of chickens. Whole-genome sequencing analysis showed that A. paragallinarum strain H18 contains an RTX toxin-like operon with strong similarity to the RTX operons of other members of the Pasteurellaceae. Four genes, designated avxIC, avxIA, avxIB, and avxID, were found in this operon. The avxIA gene encodes the structural RTX toxin-like protein, which has a predicted molecular mass of about 250 kDa. The AvxIA protein contains a peptidase S8 domain and a proprotein convertase P-domain, neither of which has been found in other RTX toxins. Recombinant AvxIA proteins expressed in Escherichia coli showed neither hemolytic nor cytotoxic activity. Polymerase chain reaction and sequencing analysis revealed that the avxIA gene was present in all strains and field isolates of A. paragallinarum examined in this study. Sera collected from chickens exposed to A. paragallinarum exhibited strong reactivity to the AvxIA protein, which suggests that AvxIA is immunogenic. This is the first report of the identification of an RTX toxin-like operon from A. paragallinarum. The gene products of this operon may be related to disease pathogenesis and potentially represent a useful vaccine target of A. paragallinarum.
Graduate Institute of Microbiology and Public Health, National Chung Hsing University, Taichung 402, Taiwan.
Yen-Chiang
YC
Pan
Duen-Huey
DH
Tan
Jui-Hung
JH
Shien
Chun-Chi
CC
Liu
Yi-Siang
YS
He
Pin-Chun
PC
Shen
Poa-Chun
PC
Chang
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001427:Bacterial Toxins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D016680:Genome, Bacterial; D008969:Molecular Sequence Data; D009876:Operon; D015661:Pasteurellaceae / Q000235:genetics* / Q000378:metabolism; D016133:Polymerase Chain Reaction / Q000379:methods; D011994:Recombinant Proteins
D001426:Bacterial Proteins; D001427:Bacterial Toxins; D011994:Recombinant Proteins