In
the sea urchin embryo spicule, there exists a proteome of >200
proteins that are responsible for controlling the mineralization of
the spicule and the formation of a fracture-resistant composite. In
this report, using recombinant proteins, we identify that two protein
components of the spicule, SM30B/C and SM50, are hydrogelators. Because
of the presence of intrinsic disorder and aggregation-prone regions,
these proteins assemble to form porous mesoscale hydrogel particles
in solution. These hydrogel particles change their size, organization,
and internal structure in response to pH and ions, particularly Ca(II),
which indicates that these behave as ion-responsive or “smart”
hydrogels. Using diffusion-ordered spectroscopy NMR, we find that
both hydrogels affect the diffusion of water, but only SM50 affects
the diffusion of an anionic solute. Thus, the extracellular matrix
of the spicule consists of several hydrogelator proteins which are
responsive to solution conditions and can control the diffusion of
water and solutes, and these proteins will serve as a model system
for designing ion-responsive, composite, and smart hydrogels.
This is a repository copy of A complicated relationship : Glycosylation, Ca(II), and primary sequence affect the interactions and kinetics between two model mollusk shell intracrystalline nacre proteins.
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