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Millisecond Hydrogen/Deuterium-Exchange Mass Spectrometry for the Study of Alpha-Synuclein Structural Dynamics Under Physiological Conditions
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Characterization of millisecond time-scale dynamics in the molten globule state of alpha-lactalbumin by NMR

S Kim1, C Bracken, J Baum

  • 1Rutgers University, Piscataway, NJ 08854, USA.

Journal of Molecular Biology
|December 28, 1999
PubMed

Insights

This study characterizes the molten globule state of alpha-lactalbumin, revealing pervasive conformational exchange dynamics. Low activation energies suggest these fluctuations are crucial for protein folding.

Area of Science:

  • Biochemistry
  • Protein Dynamics
  • Structural Biology

Background:

  • The molten globule (MG) state represents an intermediate in protein folding.
  • Understanding MG dynamics is key to elucidating folding pathways.
  • Alpha-lactalbumin's MG state exhibits complex motional dynamics.

Purpose of the Study:

  • To characterize the motional dynamics of alpha-lactalbumin's MG state.
  • To investigate conformational exchange rates and their temperature dependence.
  • To assess the energetic barriers associated with these dynamics.

Main Methods:

  • Utilized (15)N transverse relaxation rates (R2) to probe protein dynamics.
  • Employed a modified Carr-Purcell-Meiboom-Gill (CPMG) R2 pulse sequence for enhanced sensitivity.
  • Extracted chemical exchange rates by analyzing R2 as a function of CPMG delay.

Main Results:

  • Identified pervasive conformational exchange on the 0.2-0.5 ms timescale in the MG state.
  • Observed standard Arrhenius kinetic behavior for exchange rates between 10-30°C.
  • Estimated low activation energies (0.8–4.4 kcal/mol) for conformational fluctuations.

Conclusions:

  • The MG state of alpha-lactalbumin exhibits significant millisecond-timescale conformational dynamics.
  • Low energetic barriers facilitate these fluctuations, potentially guiding the transition to the native state.
  • These findings provide insights into the role of dynamic intermediates in protein folding.

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