Journal
BIOPOLYMERS
Volume 99, Issue 9, Pages 582-593Publisher
WILEY
DOI: 10.1002/bip.22218
Keywords
silk proteins; hydrodynamical properties; salts
Categories
Funding
- Natural Science and Engineering Research Council (NSERC) of Canada
- Fonds de recherche du QuebecNature et Technologies (FRQ-NT)
- Regroupement quebecois de recherche sur la fonction, la structure et l'ingenierie des proteines (PROTEO)
- Centre de recherche sur les materiaux avances (CERMA)
- Centre quebecois sur les materiaux fonctionnels (CQMF)
- Nexia Biotechnologies Inc.
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We have investigated the effect of pH, salts and shear on the hydrodynamical diameter of recombinant major ampullate (MA) rMaSpI silk proteins in solution as a function of time using 1H solution NMR spectroscopy. The results indicate that the silk proteins in solution are composed of two diffusing populations, a high proportion of native solubilized proteins and a small amount of high molecular weight oligomers. Similar results are observed with the MA gland content. Salts help maintaining the proteins in a compact form in solution over time and inhibit aggregation, the absence of salts triggering protein assembly leading to a gel state. Moreover, the aggregation kinetics of rMaSpI at low salt concentration accelerates as the pH is close to the isoelectric point of the proteins, suggesting that the pH decrease tends to slow down aggregation. The data also support the strong impact of shear on the spinning process and suggest that the assembly is driven by a nucleation conformational conversion mechanism. Thus, the adjustment of the physicochemical conditions in the ampulla seems to promote a stable, long term storage. In addition, the optimization of protein conformation as well as their unfolding and aggregation propensity in the duct leads to a specifically organized structure. (c) 2013 Wiley Periodicals, Inc. Biopolymers 99: 582-593, 2013.
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