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The osmolyte betaine promotes protein misfolding and disruption of protein aggregates
Author(s) -
Natalello Antonino,
Liu Jing,
Ami Diletta,
Doglia Silvia Maria,
de Marco Ario
Publication year - 2008
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.22266
Subject(s) - betaine , osmolyte , protein aggregation , chemistry , circular dichroism , biophysics , protein folding , dynamic light scattering , radius of gyration , hydrodynamic radius , fluorescence , fluorescence correlation spectroscopy , crystallography , biochemistry , chemical engineering , polymer , organic chemistry , molecule , nanoparticle , copolymer , biology , physics , quantum mechanics , engineering
Abstract In this work the effect of betaine on the structure and aggregation of the GST‐GFP fluorescent fusion protein was studied by different complementary techniques, including electron microscopy, dynamic light scattering, circular dichroism, and FTIR spectroscopy. Although osmolytes are known to be protein stabilizers in vivo , the effect of betaine on the structure and aggregation of our model protein was found to be strictly concentration dependent. We demonstrated that, by changing betaine concentration, it was possible to tune the formation of protein soluble assemblies and insoluble aggregates, as well as to disaggregate preformed aggregates. In particular, at a critical concentration of betaine between 5 and 7.5 m M , the protein precipitated into macroscopic prefibrillar structures, rich in intermolecular β‐sheets, which were found to bind thioflavine T and to be inaccessible to protease. Instead, at higher betaine concentration (10–20 m M ) the misfolded protein lost its fluorescence, but formed soluble assemblies with hydrodynamic radius of about 16 nm. These structures displayed a reduced propensity to further aggregate under thermal treatment. In addition, betaine at this high concentration was also found to disrupt large preformed aggregates, obtained under different conditions, into protein soluble assemblies. It is the first time that a disaggregation process has been described for a chemical chaperone. A mechanism for the betaine concentration‐dependent effect on protein misfolding, aggregation, and disaggregation is proposed and its possible physiological implications are discussed. Proteins 2009. © 2008 Wiley‐Liss, Inc.