The interaction of Staphylococcus aureus coagulase with prothrombin in various organisms

G2 Magistersavhandling, civilingenjörsavhandling


Interna författare/redaktörer


Publikationens författare: Ida Karolina Alanko
Förläggare: Åbo Akademi University
Publiceringsår: 2017


Abstrakt







Staphylococcus aureus is a commensal bacterial pathogen in humans and it causes a
variety of infectious diseases, from mild skin infections to life-threatening conditions. So-
called ‘coagulase-positive’ S. aureus strains secrete an enzyme called coagulase that
activates the central coagulation zymogen, prothrombin, without the usual proteolytic
cleavage.


It has been found that coagulase cannot activate prothrombin of Mongolian gerbil, mouse
or rat. The aim of this thesis was to examine the interaction between coagulase and
prothrombin of different organisms, especially that of gerbil, mouse and rat.


This study involved amino acid sequence analysis of different organisms’ prothrombin and
determining gerbil prothrombin sequence by means of PCR. Binding of coagulase to
prothrombin of different species was determined using monoclonal anti-polyhistidine–
agarose antibodies and studied by SDS PAGE. After determining the gene and protein
sequences for gerbil prothrombin, it was possible to construct three-dimensional models of
prothrombin-coagulase-complexes for gerbil and other organisms. The models of the
prothrombin-coagulase complexes were built by the means of homology modeling, using
an available crystal structure of the human prothrombin-coagulase complex as a template.
According to the sequence alignment, the coagulase-binding interface of prothrombin is
highly conserved and we could experimentally confirm that coagulase is able to bind to all
of the reviewed organisms’ prothrombin. Instead, the homology models suggest that the
reason why S. aureus coagulase cannot activate the rodents’ prothrombin is those subtle
changes in the prothrombin amino acid sequence that could interfere with the insertion of
coagulase N-terminal residues into the zymogen’s catalytic site.





Senast uppdaterad 2020-26-05 vid 06:24