Genomic and evolutionary analysis of novel representatives of cystatin superfamily in diverse prokaryotes
F.02 Acquisition of new scientific knowledge
COBISS.SI-ID: 37001989Three main conclusions can be drawn from our study. First, the acquisition of novel virulence factors for pathogenic bacteria by horizontal gene transfer from eukaryotes is very rare and was not analysed extensively. Second, while there is strong evidence that proteases are essential virulence factors for prokaryotic and eukaryotic parasites and pathogens during all stages of infection processes, there are very few cases where protease inhibitors have been shown to assist pathogens in invading the eukaryotic hosts by inhibiting their proteases. Third, bacterial stefins and cystatins with inhibitory spectra for diverse families of cysteine proteases are especially suited to inhibit the numerous host proteases during infection. Therefore, the bacterial stefins and cystatins are novel virulence factors that could function in the invasion and dissemination of the pathogens.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 27333415We performed a detailed functional and structural characterization of two stefins from pathogenic bacteria. Structural alignment has shown that bacterial stefins and cystatins possess both the inhibitory motif QXVXG and conserved N-terminal Gly residue. They lack however the PW or PG motif that is conserved in eukaryotic cystatins. This indicates that their modified cystatin domain has been adapted to inhibit a broad spectrum of cysteine proteases. In order to demonstrate the biochemical activity of bacterial stefins we expressed Vibrio cholerae stefin (hypothetical protein VCA0935) and Bacteroides fragilis fusion inhibitor containing chagasin and cystatin domains (hypothetical protein BF1388). We explored the inhibitory properties of recombinant VCA0935 and BF1388 proteins and determined their interaction constants with diverse cysteine proteases, cathepsins L, S, K, V, B and papain. Both VCA0935 and BF1388 were found to act as fast and tight binding inhibitors of endopeptidases cathepsins K, S, V, L and papain, however their interaction with exopeptidase cathepsin B was several orders of magnitude weaker. Interestingly, the pathogen stefins inhibits the endopeptidase activity of cathepsins S, K, L and V, which are all important players in the host adaptive and innate immunity.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 27092519