Native-unlike long-lived intermediates along the folding pathway of the amyloidogenic protein beta2-microglobulin revealed by real-time two-dimensional NMR

J Biol Chem. 2010 Feb 19;285(8):5827-35. doi: 10.1074/jbc.M109.061168. Epub 2009 Dec 22.

Abstract

Beta2-microglobulin (beta2m), the light chain of class I major histocompatibility complex, is responsible for the dialysis-related amyloidosis and, in patients undergoing long term dialysis, the full-length and chemically unmodified beta2m converts into amyloid fibrils. The protein, belonging to the immunoglobulin superfamily, in common to other members of this family, experiences during its folding a long-lived intermediate associated to the trans-to-cis isomerization of Pro-32 that has been addressed as the precursor of the amyloid fibril formation. In this respect, previous studies on the W60G beta2m mutant, showing that the lack of Trp-60 prevents fibril formation in mild aggregating condition, prompted us to reinvestigate the refolding kinetics of wild type and W60G beta2m at atomic resolution by real-time NMR. The analysis, conducted at ambient temperature by the band selective flip angle short transient real-time two-dimensional NMR techniques and probing the beta2m states every 15 s, revealed a more complex folding energy landscape than previously reported for wild type beta2m, involving more than a single intermediate species, and shedding new light into the fibrillogenic pathway. Moreover, a significant difference in the kinetic scheme previously characterized by optical spectroscopic methods was discovered for the W60G beta2m mutant.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Substitution
  • Amyloid / chemistry*
  • Amyloid / genetics
  • Humans
  • Kinetics
  • Mutation, Missense
  • Nuclear Magnetic Resonance, Biomolecular
  • Protein Folding*
  • beta 2-Microglobulin / chemistry*
  • beta 2-Microglobulin / genetics

Substances

  • Amyloid
  • beta 2-Microglobulin