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Conformations within soluble oligomers and insoluble aggregates revealed by resonance energy transfer
Author(s) -
Digambaranath Jyothi L.,
Dang Loan,
Dembinska Monika,
Vasyluk Andrew,
Finke John M.
Publication year - 2010
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.21324
Subject(s) - chemistry , oligomer , monomer , circular dichroism , acceptor , förster resonance energy transfer , crystallography , dimer , peptide , polymer , biophysics , stereochemistry , polymer chemistry , biochemistry , fluorescence , organic chemistry , physics , quantum mechanics , condensed matter physics , biology
A fluorescently labeled 20‐residue polyglutamic acid (polyE) peptide 20 amino acid length polyglutamic acid (E 20 ) was used to study structural changes which occur in E 20 as it co‐aggregates with other unlabeled polyE peptides. Resonance energy transfer (RET) was performed using an o ‐aminobenzamide donor at the N‐terminus and 3‐nitrotyrosine acceptor at the C‐terminus of E 20 . PolyE aggregates were not defined as amyloid, as they were nonfibrillar and did not bind congo red. Circular dichroism measurements indicate that polyE aggregation involves a transition from α‐helical monomers to aggregated β‐sheets. Soluble oligomers are also produced along with aggregates in the reaction, as determined through size exclusion chromatography. Time‐resolved and steady‐state RET measurements reveal four dominant E 20 conformations: (1) a partially collapsed conformation (24 Å donor–acceptor distance) in monomers, (2) an extended conformation in soluble oligomers (>29 Å donor–acceptor distance), (3) a minor partially collapsed conformation (22 Å donor‐acceptor distance) in aggregates, and (4) a major highly collapsed conformation (13 Å donor–acceptor distance) in aggregates. These findings demonstrate the use of RET as a means of determining angstrom‐level structural details of soluble oligomer and aggregated states of proteins. © 2009 Wiley Periodicals, Inc. Biopolymers 93: 299–317, 2010. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com