molecular biology Molecular biology is the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including biomolecular synthesis, modification, mechanisms, and interactions. The study of chemical and physi ...

, pertactin (PRN) is a highly immunogenic

virulence factor Virulence factors (preferably known as pathogenicity factors or effectors in plant science) are cellular structures, molecules and regulatory systems that enable microbial pathogens (bacteria, viruses, fungi, and protozoa) to achieve the following ...

of ''

Bordetella pertussis ''Bordetella pertussis'' is a Gram-negative, aerobic, pathogenic, encapsulated coccobacillus of the genus ''Bordetella'', and the causative agent of pertussis or whooping cough. Like '' B. bronchiseptica'', ''B. pertussis'' is motile and expre ...

'', the

bacterium Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were amon ...

that causes

pertussis Whooping cough, also known as pertussis or the 100-day cough, is a highly contagious bacterial disease. Initial symptoms are usually similar to those of the common cold with a runny nose, fever, and mild cough, but these are followed by two or t ...

. Specifically, it is an outer

membrane protein Membrane proteins are common proteins that are part of, or interact with, biological membranes. Membrane proteins fall into several broad categories depending on their location. Integral membrane proteins are a permanent part of a cell membrane ...

that promotes

adhesion Adhesion is the tendency of dissimilar particles or surfaces to cling to one another ( cohesion refers to the tendency of similar or identical particles/surfaces to cling to one another). The forces that cause adhesion and cohesion can b ...

trachea The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air- breathing animals with lungs. The trachea extends from the ...

l epithelial cells. PRN is purified from ''Bordetella pertussis'' and is used for the vaccine production as one of the important components of acellular pertussis vaccine. A large part of the N-terminus of the pertactin protein is composed of

beta helix A beta helix is a tandem protein repeat structure formed by the association of parallel beta strands in a helical pattern with either two or three faces. The beta helix is a type of solenoid protein domain. The structure is stabilized by inter- ...

repeats. This region of the pertactin protein is secreted through the C-terminal autotransporter. The N-terminal signal sequences promotes the secretion of PRN into the periplasm through the bacterial secretion system (Sec) and consequently, the translocation into the outer membrane where it is proteolytically cleaved. The loops in the right handed β-helix of the N-terminus that protrudes out of cell surface (region R1) contains sequence repeats Gly-Gly-Xaa-Xaa-Pro and the RGD domain Arg-Gly-Asp. This RGD domain allows PRN to function as an adhesin and

invasin Invasins are a class of proteins associated with the penetration of pathogens into host cells. Invasins play a role in promoting entry during the initial stage of infection. In 2007, Als3 was identified as a fungal invasion allowing ''Candida alb ...

, binding to integrins on the outer membrane of the cell. Another loop of the extending β-helix is region 2 (R2) which contains Pro-Gln-Pro (PQP) repeats towards the C-terminus. This protein’s contribution to immunity is still premature. Reports suggest that R1 and R2 are immunogenic regions, however, recent studies regarding genetic variation of those regions prove otherwise.

In ''B.bronchiseptica''

Pertactin adheres to only ciliated epithelial cells of ''B. bronchiseptica'' ''in vivo''. However, ''in vitro'', PRN does not adhere to either. PRN does however help provide resistance towards a hyperinflammatory response of innate immunity for ''B. bronchiseptica.'' With respect to the adaptive immunity, studies show that PRN plays a role in combating neutrophil-mediated clearance of ''B. bronchiseptica.''

References

Bacteriology Virulence factors Whooping cough {{biochem-stub