In
molecular biology, pertactin (PRN) is a highly immunogenic
virulence factor of ''
Bordetella pertussis'', the
bacterium that causes
pertussis. Specifically, it is an outer
membrane protein that promotes
adhesion to
tracheal
epithelial cell
Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellula ...
s. 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
The N-terminus (also known as the amino-terminus, NH2-terminus, N-terminal end or amine-terminus) is the start of a protein or polypeptide, referring to the free amine group (-NH2) located at the end of a polypeptide. Within a peptide, the ami ...
of the pertactin protein is composed of
beta helix 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, 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
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