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Title: Solution Structure of an Amyloid-Forming Protein During Photoinitiated Hexamer-Dodecamer Transitions Revealed Through Small-Angle Neutron Scattering

Abstract

Shape-reconstruction analysis applied to small angle neutron scattering (SANS) data is used to determine the in vitro conformations of {alpha}-chymotrypsin oligomers that form as a result of partial unfolding with a photoresponsive surfactant. In the presence of the photoactive surfactant under visible light, the native oligomers (dimers or compact hexamers) rearrange into expanded corkscrew-like hexamers. Converting the surfactant to the photopassive form with UV light illumination causes the hexamers to laterally aggregate and intertwine into dodecamers with elongated, twisted conformations containing cross-sectional dimensions similar to amyloid protofilaments. Secondary-structure measurements with FT-IR indicate that this photoinduced hexamer-to-dodecamer association occurs through intermolecular {beta} sheets stabilized with hydrogen bonds, similar to amyloid formation. Traditional structural characterization techniques such as X-ray crystallography and NMR are not easily amenable to the study of these non-native protein conformations; however, SANS is ideally suited to the study of these associated intermediates, providing direct observation of the mechanism of oligomeric formation in an amyloid-forming protein. Combined with photoinitiated hexamer-to-dodecamer associations in the presence of the photoresponsive surfactant, this study could provide unique insight into the amyloidosis disease pathway, as well as novel disease treatment strategies.

Authors:
; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
929942
Report Number(s):
BNL-80537-2008-JA
Journal ID: ISSN 0006-2960; TRN: US200822%%1111
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Biochemistry; Journal Volume: 46
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; 36 MATERIALS SCIENCE; CRYSTALLOGRAPHY; CRYSTAL STRUCTURE; DIMERS; DISEASES; HYDROGEN; ILLUMINANCE; IN VITRO; NEUTRONS; NUCLEAR MAGNETIC RESONANCE; PROTEINS; SCATTERING; SHEETS; SURFACTANTS; VISIBLE RADIATION; X-RAY DIFFRACTION; national synchrotron light source

Citation Formats

Hamill,A., Wang, S., and Lee, Jr., C.. Solution Structure of an Amyloid-Forming Protein During Photoinitiated Hexamer-Dodecamer Transitions Revealed Through Small-Angle Neutron Scattering. United States: N. p., 2007. Web. doi:10.1021/bi700233k.
Hamill,A., Wang, S., & Lee, Jr., C.. Solution Structure of an Amyloid-Forming Protein During Photoinitiated Hexamer-Dodecamer Transitions Revealed Through Small-Angle Neutron Scattering. United States. doi:10.1021/bi700233k.
Hamill,A., Wang, S., and Lee, Jr., C.. Mon . "Solution Structure of an Amyloid-Forming Protein During Photoinitiated Hexamer-Dodecamer Transitions Revealed Through Small-Angle Neutron Scattering". United States. doi:10.1021/bi700233k.
@article{osti_929942,
title = {Solution Structure of an Amyloid-Forming Protein During Photoinitiated Hexamer-Dodecamer Transitions Revealed Through Small-Angle Neutron Scattering},
author = {Hamill,A. and Wang, S. and Lee, Jr., C.},
abstractNote = {Shape-reconstruction analysis applied to small angle neutron scattering (SANS) data is used to determine the in vitro conformations of {alpha}-chymotrypsin oligomers that form as a result of partial unfolding with a photoresponsive surfactant. In the presence of the photoactive surfactant under visible light, the native oligomers (dimers or compact hexamers) rearrange into expanded corkscrew-like hexamers. Converting the surfactant to the photopassive form with UV light illumination causes the hexamers to laterally aggregate and intertwine into dodecamers with elongated, twisted conformations containing cross-sectional dimensions similar to amyloid protofilaments. Secondary-structure measurements with FT-IR indicate that this photoinduced hexamer-to-dodecamer association occurs through intermolecular {beta} sheets stabilized with hydrogen bonds, similar to amyloid formation. Traditional structural characterization techniques such as X-ray crystallography and NMR are not easily amenable to the study of these non-native protein conformations; however, SANS is ideally suited to the study of these associated intermediates, providing direct observation of the mechanism of oligomeric formation in an amyloid-forming protein. Combined with photoinitiated hexamer-to-dodecamer associations in the presence of the photoresponsive surfactant, this study could provide unique insight into the amyloidosis disease pathway, as well as novel disease treatment strategies.},
doi = {10.1021/bi700233k},
journal = {Biochemistry},
number = ,
volume = 46,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • We have characterized micelle structure and intermicelle interaction for the detergents lauryldimethylamine N-oxide, LDAO, and n-octyl-[beta]-D-glucoside, OG, under conditions used for protein crystallization using SANS. We found that LDAO and OG micelles differ significantly in size, sensitivity to heptanetriol, and nature of intermicelle interactions. Our results suggest that successful crystallization methods can be rationalized in terms of an optimization of micelle size, number density, flexibility of micelle radius of curvature, and suppression of intermicelle interactions. LDAO and OG micelles were found to differ significantly in size and shape. The LDAO micelle was found to be best fit as an ellipsoidmore » with semiaxes of 30.6 and 19.4 [angstrom], while the OG micelle was found to be spherical with a radius of 22.9 [angstrom]. The addition of heptanetriol to pure LDAO resulted in the formation of smaller, spherical, mixed micelles with radii in the range 17-21 [angstrom], depending upon conditions. The results suggest that both micelle size and curvature restrictions may contribute to the incompatibility of LDAO for protein crystallization in the absence of additional amphiphiles. 32 refs., 8 figs., 3 tabs.« less
  • No abstract prepared.
  • Solution scattering of neutrons and x-rays can provide direct information on local interactions of importance for biomolecular folding and structure. Here, neutron scattering experiments are combined with molecular-dynamics simulation to interpret the scattering signal of a series of dipeptides with varying degrees of hydrophobicity (GlyAla, GlyPro, and AlaPro) in concentrated aqueous solution (1:20 solute/water ratio) in which the peptides form large segregates (up to 50 60 amino acids). Two main results are found: 1), the shift to lower Q of the so-called water-ring peak (Q ≈ 2Å –1) arises mainly from an overlap of water-peptide and peptide-peptide correlations in themore » region of 1.3 < Q < 2Å –1 , rather than from a shift of the water signal induced by the presence of the clusters; and 2), in the low-Q region (Q ≈ 0.6Å –1) a positive peak is observed originating from both the solute-solute correlations and changes in the water structure induced by the formation of the clusters. In particular, the water molecules are found to be more connected than in the bulk with hydrogen-bonding directions tangential to the exposed hydrophobic surfaces, and this effect increases with increasing peptide hydrophobicity. Lastly, this work demonstrates that important information on the (hydrophobic) hydration of biomolecules can be obtained in the very-small-angle region.« less
  • Small-angle neutron scattering measurements in dilute solution were performed on the Mcg Bence-Jones protein dimer, for which accurate atomic coordinates have been determined by crystallographic methods. The measured radius of gyration (R/sub g/) in H/sub 2/O buffer is 24.0 +/- 0.4 angstrom and in D/sub 2/O buffer is 23.3 +/- O.1 angstrom; the calculated value of R/sub v/ (R/sub g/ in vacuo) is 24.0 angstrom. On the basis of a match point of 44.2% D/sub 2/O concentration, the experimental partial specific volume is 0.74 cm/sup 3//g. The experimentally derived molecular weight of 47 000 is in very good agreement withmore » that (45 500) calculated from the amino acid composition. For comparisons with different Fab's (antigen binding fragments) exhibiting various ''elbow bends'' due to the flexibility of the switch peptide between variable and constant domains of the immunoglobulin chains, calculation of the R/sub g/ value of the Mcg dimer was performed as a function of the elbow bend. The R/sub g/ varied from 22.8 to 26.0 angstrom as the elbow bend was opened from 100/sup 0/ to 180/sup 0/; the maximum radius of gyration of the particle was 26.5 angstrom with the switch peptide stretched by separating the variable and constant domains by an additional 1.5 angstrom at an elbow bend of 180/sup 0/.« less