skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Unfolding bovine α-lactalbumin with T-jump: Characterizing disordered intermediates via time-resolved x-ray solution scattering and molecular dynamics simulations

Journal Article · · Journal of Chemical Physics
DOI:https://doi.org/10.1063/5.0039194· OSTI ID:1813292

The protein folding process often proceeds through partially folded transient states. Therefore, a structural understanding of these disordered states is crucial for developing mechanistic models of the folding process. Characterization of unfolded states remains challenging due to their disordered nature, and incorporating multiple methods is necessary. Combining the time-resolved x-ray solution scattering (TRXSS) signal with molecular dynamics (MD), we are able to characterize transient partially folded states of bovine α-lactalbumin, a model system widely used for investigation of molten globule states, during its unfolding triggered by a temperature jump. We track the unfolding process between 20 μs and 70 ms and demonstrate that it passes through three distinct kinetic states. The scattering signals associated with these transient species are then analyzed with TRXSS constrained MD simulations to produce protein structures that are compatible with the input signals. Without utilizing any experimentally extracted kinetic information, the constrained MD simulation successfully drove the protein to an intermediate molten globule state; signals for two later disordered states are refined to terminal unfolded states. From our examination of the structural characteristics of these disordered states, we discuss the implications disordered states have on the folding process, especially on the folding pathway. Finally, we discuss the potential applications and limitations of this method.

Research Organization:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Organization:
USDOE; National Institutes of Health (NIH)
Grant/Contract Number:
AC02-06CH11357; R01-GM115761; 5T32GM008382; SC0000989
OSTI ID:
1813292
Journal Information:
Journal of Chemical Physics, Vol. 154, Issue 10; ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)Copyright Statement
Country of Publication:
United States
Language:
English

References (70)

Protein folding studied by single-molecule FRET journal February 2008
Probing Cytochrome c Folding Transitions upon Phototriggered Environmental Perturbations Using Time-Resolved X-ray Scattering journal April 2018
Rapid mixing stopped-flow small-angle X-ray scattering study of lipoplex formation at beamline ID02@ESRF journal January 2015
Ab initio electron density determination directly from solution scattering data journal January 2018
Crystal Structures of Apo- and Holo-bovine α-Lactalbumin at 2.2-Å Resolution Reveal an Effect of Calcium on Inter-lobe Interactions journal November 2000
Structure and Dynamics of the α-Lactalbumin Molten Globule:  Fluorescence Studies Using Proteins Containing a Single Tryptophan Residue journal June 2001
Scalable molecular dynamics with NAMD journal January 2005
Bayesian ensemble refinement by replica simulations and reweighting journal December 2015
Fast events in protein folding initiated by nanosecond laser photolysis. journal December 1993
Structure and Dynamics of an Unfolded Protein Examined by Molecular Dynamics Simulation journal February 2012
Numerical integration of the cartesian equations of motion of a system with constraints: molecular dynamics of n-alkanes journal March 1977
Tracking reaction dynamics in solution by pump–probe X-ray absorption spectroscopy and X-ray liquidography (solution scattering) journal January 2016
Zerstreuung von Röntgenstrahlen journal January 1915
Conformational ensemble of native α-synuclein in solution as determined by short-distance crosslinking constraint-guided discrete molecular dynamics simulations journal March 2019
Intrinsic Conformational Preferences and Interactions in α-Synuclein Fibrils: Insights from Molecular Dynamics Simulations journal May 2018
Thermal unfolding of bovine alpha-lactalbumin. Comparison of circular dichroism with hydrophobicity measurements. journal March 1994
Detailed Transient Heme Structures of Mb-CO in Solution after CO Dissociation: An X-ray Transient Absorption Spectroscopic Study journal November 2012
Impulsive solvent heating probed by picosecond x-ray diffraction journal March 2006
Accurate SAXS Profile Computation and its Assessment by Contrast Variation Experiments journal August 2013
Bipartite structure of the α-lactalbumin molten globule journal April 1995
Native contacts determine protein folding mechanisms in atomistic simulations journal October 2013
Hydrogen exchange mass spectrometry for studying protein structure and dynamics journal January 2011
An arsenal of methods for the experimental characterization of intrinsically disordered proteins – How to choose and combine them? journal November 2019
CHARMM36m: an improved force field for folded and intrinsically disordered proteins journal November 2016
Compact state of a protein molecule with pronounced small-scale mobility: bovine ?-lactalbumin journal December 1985
Equilibrium and kinetics of the thermal unfolding of α-lactalbumin. The relation to its folding mechanism journal July 1978
Real-time tracking of protein unfolding with time-resolved x-ray solution scattering journal September 2020
Statistical Mechanics of the Denatured State of a Protein Using Replica-Averaged Metadynamics journal June 2014
Protein Structural Dynamics Revealed by Time-Resolved X-ray Solution Scattering journal July 2015
Dynamics of Quaternary Structure Transitions in R-State Carbonmonoxyhemoglobin Unveiled in Time-Resolved X-ray Scattering Patterns Following a Temperature Jump journal September 2018
SAXS-Restrained Ensemble Simulations of Intrinsically Disordered Proteins with Commitment to the Principle of Maximum Entropy journal August 2019
When fast is better: protein folding fundamentals and mechanisms from ultrafast approaches journal August 2016
Calcium Triggered Lα-H2 Phase Transition Monitored by Combined Rapid Mixing and Time-Resolved Synchrotron SAXS journal April 2008
Extended experimental inferential structure determination method in determining the structural ensembles of disordered protein states journal June 2020
Conserved Folding Pathways of α-Lactalbumin and Lysozyme Revealed by Kinetic CD, Fluorescence, NMR, and Interrupted Refolding Experiments journal May 2008
Deciphering Solution Scattering Data with Experimentally Guided Molecular Dynamics Simulations journal January 2015
Time-Resolved Circular Dichroism Studies of Protein Folding Intermediates of Cytochrome c journal April 1998
Protein folding from heterogeneous unfolded state revealed by time-resolved X-ray solution scattering journal June 2020
SAXS-Guided Metadynamics journal June 2015
Introduction to Intrinsically Disordered Proteins (IDPs) journal July 2014
Combining prediction, computation and experiment for the characterization of protein disorder journal October 2004
Restoring Low Resolution Structure of Biological Macromolecules from Solution Scattering Using Simulated Annealing journal June 1999
Revealing Fast Structural Dynamics in pH-Responsive Peptides with Time-Resolved X-ray Scattering journal February 2019
New analytical scattering-factor functions for free atoms and ions journal May 1995
Fast protein folding kinetics journal March 2014
Effect of ethanol on insulin dimer dissociation journal February 2019
Picosecond Photobiology: Watching a Signaling Protein Function in Real Time via Time-Resolved Small- and Wide-Angle X-ray Scattering journal July 2016
Integrating solvation shell structure in experimentally driven molecular dynamics using x-ray solution scattering data journal May 2020
Fast Compaction of α-Lactalbumin During Folding Studied by Stopped-flow X-ray Scattering journal August 2002
Low Resolution Solution Structure of HAMLET and the Importance of Its Alpha-Domains in Tumoricidal Activity journal December 2012
Temperature-jump solution X-ray scattering reveals distinct motions in a dynamic enzyme journal September 2019
Martini bead form factors for nucleic acids and their application in the refinement of protein–nucleic acid complexes against SAXS data journal March 2019
Rapid collapse and slow structural reorganisation during the refolding of bovine α-lactalbumin journal May 1999
Evidence for identity between the equilibrium unfolding intermediate and a transient folding intermediate: a comparative study of the folding reactions of .alpha.-lactalbumin and lysozyme journal November 1986
Using collective variables to drive molecular dynamics simulations journal December 2013
CHARMM TIP3P Water Model Suppresses Peptide Folding by Solvating the Unfolded State journal April 2016
Direct Observation of Insulin Association Dynamics with Time-Resolved X-ray Scattering journal September 2017
Replica-exchange molecular dynamics method for protein folding journal November 1999
Studying Protein–Protein Binding through T-Jump Induced Dissociation: Transient 2D IR Spectroscopy of Insulin Dimer journal May 2016
Signal amplification and transduction in phytochrome photosensors journal April 2014
X-ray snapshots reveal conformational influence on active site ligation during metalloprotein folding journal January 2019
Tracking the structural dynamics of proteins in solution using time-resolved wide-angle X-ray scattering journal September 2008
A smooth particle mesh Ewald method journal November 1995
Interpretation of Solution X-Ray Scattering by Explicit-Solvent Molecular Dynamics journal May 2015
Escaping free-energy minima journal September 2002
Atomic-level description of ubiquitin folding journal March 2013
BioCARS: a synchrotron resource for time-resolved X-ray science journal May 2011
Atomic-level characterization of disordered protein ensembles journal February 2007
VMD: Visual molecular dynamics journal February 1996
Rapid formation of a molten globule intermediate in refolding of α-lactalbumin journal August 1996