M.Kotsyfakis
et al.
(2010).
The crystal structures of two salivary cystatins from the tick Ixodes scapularis and the effect of these inhibitors on the establishment of Borrelia burgdorferi infection in a murine model.
Mol Microbiol,
77,
456-470.
PubMed id: 20545851
The crystal structures of two salivary cystatins from the tick Ixodes scapularis and the effect of these inhibitors on the establishment of Borrelia burgdorferi infection in a murine model.
M.Kotsyfakis,
H.Horka,
J.Salat,
J.F.Andersen.
ABSTRACT
Summary We have previously demonstrated that two salivary cysteine protease
inhibitors from the Borrelia burgdorferi (Lyme disease) vector Ixodes scapularis
-namely sialostatins L and L2- play an important role in tick biology, as
demonstrated by the fact that silencing of both sialostatins in tandem results
in severe feeding defects. Here we show that sialostatin L2 -but not sialostatin
L- facilitates the growth of Borrelia burgdorferi in murine skin. To examine the
structural basis underlying these differential effects of the two sialostatins,
we have determined the crystal structures of both sialostatin L and L2. This is
the first structural analysis of cystatins from an invertebrate source.
Sialostatin L2 crystallizes as a monomer with an 'unusual' conformation of the
N-terminus, while sialostatin L crystallizes as a domain-swapped dimer with an
N-terminal conformation similar to other cystatins. Deletion of the 'unusual'
N-terminal five residues of sialostatin L2 results in marked changes in its
selectivity, suggesting that this region is a particularly important determinant
of the biochemical activity of sialostatin L2. Collectively, our results reveal
the structure of two tick salivary components that facilitate vector blood
feeding and that one of them also supports pathogen transmission to the
vertebrate host.
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