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The controlling roles of Trp60 and Trp95 in beta2-microglobulin function, folding and amyloid aggregation properties

Gennaro Esposito1, Stefano Ricagno, Alessandra Corazza

  • 1Department of Biomedical Science and Technology, University of Udine, Piazzale Kolbe 4, 33100 Udine, Italy.

Journal of Molecular Biology
|April 9, 2008
PubMed

Insights

Altering specific tryptophan residues in beta(2)-microglobulin (beta(2)m) impacts its amyloid formation and function. Trp60 stabilizes beta(2)m and reduces amyloid propensity, while Trp95 is crucial for structural integrity.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Protein Chemistry

Background:

  • Dialysis-associated amyloidosis stems from elevated beta(2)-microglobulin (beta(2)m) levels.
  • beta(2)m is inherently amyloidogenic, with aggregation influenced by concentration.
  • No human genetic variants of beta(2)m are known.

Purpose of the Study:

  • To investigate the roles of conserved Tryptophan (Trp) residues (Trp60 and Trp95) in beta(2)m structure, function, and folding/misfolding.
  • To understand how mutations at these sites affect beta(2)m's amyloidogenic potential and its interaction with MHC.

Main Methods:

  • Combined biophysical and functional analyses were employed.
  • Site-directed mutagenesis (Trp60-->Gly and Trp95-->Gly) was performed.
  • Interactions with Class I Major Histocompatibility Complex (MHC) heavy chains were assessed.

Main Results:

  • Trp60 is crucial for beta(2)m association with Class I MHC and its mutation stabilizes beta(2)m, reduces amyloid propensity, and weakens MHC binding.
  • Trp95 is buried in the core; its mutation destabilizes beta(2)m, leading to unfolded protein and non-fibrillar aggregates.
  • Trp60 and Trp95 play distinct roles in beta(2)m structure, function, and aggregation.

Conclusions:

  • Trp60 is vital for beta(2)m function and modulates amyloid formation.
  • Trp95 is essential for maintaining beta(2)m structural stability.
  • Targeting these Trp residues offers insights into preventing beta(2)m amyloidosis.

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