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beta2-microglobulin H31Y variant 3D structure highlights the protein natural propensity towards intermolecular

C Rosano1, S Zuccotti, P Mangione

  • 1Istituto Nazionale Ricerca sul Cancro-IST, X-ray Structural Biology Unit, Largo Rosanno Benzi 10, 16132 Genova, Italy.

Journal of Molecular Biology
|December 31, 2003
PubMed

Insights

A novel human beta2-microglobulin (beta2m) mutant, His31-->Tyr, exhibits enhanced stability and accelerated folding. This mutant displays structural features and molecular packing consistent with amyloidogenic properties, offering insights into protein misfolding diseases.

Area of Science:

  • Biochemistry
  • Structural Biology
  • Molecular Medicine

Background:

  • Beta2-microglobulin (beta2m) is the light chain of human class I major histocompatibility complex (MHC-I).
  • Renal failure and hemodialysis can lead to elevated beta2m levels, causing amyloid fibril deposition.
  • Protein stability and folding dynamics are crucial for understanding beta2m-associated pathologies.

Purpose of the Study:

  • To characterize the structural and folding properties of the His31-->Tyr human beta2m mutant.
  • To investigate the molecular basis of the mutant's enhanced stability and amyloidogenic potential.
  • To elucidate the role of specific structural features and molecular packing in protein assembly.

Main Methods:

  • X-ray crystallography at 2.9A resolution to determine the mutant's three-dimensional structure.
  • Nuclear Magnetic Resonance (NMR) spectroscopy for detailed molecular characterization.
  • Analysis of protein-protein interactions and hydrogen bonding within the crystal structure.

Main Results:

  • The His31-->Tyr mutant demonstrates a ten-fold faster slow phase of folding compared to wild-type beta2m.
  • Crystal structure reveals a compact protein assembly stabilized by intermolecular interactions and hydrogen bonds.
  • Observed conformational heterogeneity and N-terminal beta-strand unpairing in one protomer suggest amyloidogenic propensity.

Conclusions:

  • The His31-->Tyr beta2m mutant exhibits increased stability and altered folding kinetics.
  • Specific structural features and crystal packing contribute to a stable, yet potentially amyloidogenic, protein assembly.
  • This mutant serves as a valuable model for studying the structural underpinnings of beta2m amyloidosis.

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