| Type: | Family | Name: | Bordetella pertussis toxin B |
| Description: | A large group of bacterial exotoxins are referred to as "A/B toxins", essentially because they are formed from two subunits []. The "A" subunitpossesses enzyme activity, and is transferred to the host cell following a conformational change in the membrane-bound transport "B" subunit [].Bordetella pertussisis the causative agent of whooping cough, and is a Gram-negative aerobic coccus. Its major virulence factor is the pertussis toxin, an A/B exotoxin that mediates both colonisation and toxaemic stages of the the disease [, ]. Recombinant, inactive forms of the 5 subunits that make up the toxin have proven to be good vaccines. The S2 and S3 subunits of the toxin form part of the "B" moiety. They are responsible for binding the whole toxin to host cells prior to invasion, and are classed as adhesins []. S2 attaches to a host receptor called lactosylceramide. It has also been speculated that the S3 unit may preferentially bind phagocytes.The crystal structure of pertussis toxin has been determined to 2.9A resolution []. The catalytic A-subunit (S1) shares structural similarity with other ADP-ribosylating bacterial toxins, although differences in the C-terminal portion explain its unique activation mechanism. Despite itsheterogeneous subunit composition, the structure of the cell-binding B-oligomer (S2, S3, two copies of S4, and S5) resembles the symmetricalB-pentamers of the cholera and shiga toxin families, but it interacts differently with the A-subunit and there is virtually no sequence similarity between B-subunits of the different toxins. Two peripheral domains that are unique to the pertussis toxin B-oligomer share structural similarity with a calcium-dependent eukaryotic lectin, and reveal possible receptor-binding sites. | Short Name: | ToxinB_BORPE |
