2 research outputs found
Hierarchical Assembly of Tough Bioelastomeric Egg Capsules is Mediated by a Bundling Protein
Marine snail egg
capsules are shock-absorbing bioelastomers made
from precursor “egg case proteins” (ECPs) that initially
lack long-range order. During capsule formation, these proteins self-assemble
into coiled-coil filaments that subsequently align into microscopic
layers, a multiscale process which is crucial to the capsules’
shock-absorbing properties. In this study, we show that the self-assembly
of ECPs into their functional capsule material is mediated by a bundling
protein that facilitates the aggregation of coiled-coil building blocks
and their gelation into a prefinal capsule prior to final stabilization.
This low molecular weight bundling protein, termed Pugilina cochlidium Bundling Protein (PcBP), led
to gelation of native extracts from gravid snails, whereas crude extracts
lacking PcBP did not gelate and remained as a protein solution. Refolding
and reconcentration of recombinant PcBP induced bundling and aggregation
of ECPs, as evidenced by ECPs oligomerization. We propose that the
secretion of PcBP <i>in vivo</i> is a time-specific event
during the embryo encapsulation process prior to cross-linking in
the ventral pedal gland (VPG). Using molecular dynamics (MD) simulations,
we further propose plausible disulfide binding sites stabilizing two
PcBP monomers, as well as a polarized surface charge distribution,
which we suggest plays an important role in the bundling mechanism.
Overall, this study shows that controlled bundling is a key step during
the extra-cellular self-assembly of egg capsules, which has previously
been overlooked
Biomimetic Production of Silk-Like Recombinant Squid Sucker Ring Teeth Proteins
The
sucker ring teeth (SRT) of Humboldt squid exhibit mechanical
properties that rival those of robust engineered synthetic polymers.
Remarkably, these properties are achieved without a mineral phase
or covalent cross-links. Instead, SRT are exclusively made of silk-like
proteins called “suckerins”, which assemble into nanoconfined
β-sheet reinforced supramolecular networks. In this study, three
streamlined strategies for full-length recombinant suckerin protein
production and purification were developed. Recombinant suckerin exhibited
high solubility and colloidal stability in aqueous-based solvents.
In addition, the colloidal suspensions exhibited a concentration-dependent
conformational switch, from random coil to β-sheet enriched
structures. Our results demonstrate that recombinant suckerin can
be produced in a facile manner in E. coli and processed from mild aqueous solutions into materials enriched
in β-sheets. We suggest that recombinant suckerin-based materials
offer potential for a range of biomedical and engineering applications