Identification and characterization of the TonB region and its role in transferrin-mediated iron acquisition inHaemophilus parasuis

Abstract

Haemophilus parasuis is the causative agent of Glässer's disease, which is responsible for considerable economic losses in the pig-rearing industry. The aim of the study reported here was the identification, sequencing and molecular characterization of the TonB region that includes tonB, exbBD, and tbpBA genes in H. parasuis. In addition, two fusion proteins were generated. One of them (pGEX-6P-1-GST-TbpB) contained the first 501 amino acids of H. parasuis TbpB protein, while the second (pBAD-Thio-TbpB-V5-His) included the first 102 amino acids of H. parasuis TbpB N-terminus domain. A panel of 14 hybridomas secreting monoclonal antibodies was raised against the two recombinant TbpB fusion proteins. Furthermore, to assess whether the expression of the H. parasuis ExbB, TbpB, and TbpA proteins was upregulated under conditions of restricted availability of iron, a rabbit polyclonal antibody against H. parasuis TbpB-His fusion protein was produced. A rabbit polyclonal antibody against serotype 7 of Actinobacillus pleuropneumoniae ExbB and TbpA proteins was also used for the detection of the homologous proteins in H. parasuis. Overall, the data indicate that H. parasuis, like other members of the Pasteurellaceae family, possesses the genetic elements of the TonB region for iron acquisition and the transferrin-binding proteins encoded under this region are upregulated under restricted iron availability.

Genomic Characterization of Haemophilus parasuis SH0165, a Highly Virulent Strain of Serovar 5 Prevalent in China

“…Two clusters of consecutive genes exbB1 – exbD1 – tonB1 (257 aa) (HAPS1366–1364) and tonB2 (267 aa)– exbB2 – exbD2 (HAPS2220–2222) were identified in the SH0165 genome, which are responsible for the formation of the TonB1 and TonB2 systems, respectively. Gene components of the TonB2 system have been described previously in H. parasuis [9]. Although the periplasmic proteins TonB1 and TonB2 share low sequence identity (24%), they contain an identical domain (PF03544) involved in the transfer of energy to transferrin binding proteins (TbpB and TbpA), both homologues of which are responsible for transport of iron across the outer membrane of A. pleuropneumoniae [76].…”

New insights about functional and cross-reactive properties of antibodies generated against recombinant TbpBs of Haemophilus parasuis

“…H. parasuis , Actinobacillus pleuropneumoniae and A. suis possess surface receptors that enable them to acquire iron from the host iron-binding protein transferrin (Tf) 5 – 7 . The surface receptor is comprised of an integral outer membrane protein, Tf binding protein A (TbpA), and a membrane-anchored surface lipoprotein, Tf binding protein B (TbpB).…”

Pan-genome wide association study of Glaesserella parasuis highlights genes associated with virulence and biofilm formation

“…Transferrin-binding protein plays an essential role in iron acquisition ( Moraes et al, 2009 ; Calmettes et al, 2012 ). Pathogenic bacteria can use high-affinity iron uptake systems, such as transferrin-binding proteins, to capture the iron of the host ( del Río et al, 2005 ; Curran et al, 2015 ). Similarly, transferrin-binding protein expression is beneficial to maintaining bacteria survival under low iron conditions, such as within biofilm.…”