The roles of helix I and strand 5A in the folding, function and misfolding of α1-antitrypsin

PLoS One. 2013;8(1):e54766. doi: 10.1371/journal.pone.0054766. Epub 2013 Jan 29.

Abstract

α(1)-Antitrypsin, the archetypal member of the serpin superfamily, is a metastable protein prone to polymerization when exposed to stressors such as elevated temperature, low denaturant concentrations or through the presence of deleterious mutations which, in a physiological context, are often associated with disease. Experimental evidence suggests that α(1)-Antitrypsin can polymerize via several alternative mechanisms in vitro. In these polymerization mechanisms different parts of the molecule are proposed to undergo conformational change. Both strand 5 and helix I are proposed to adopt different conformations when forming the various polymers, and possess a number of highly conserved residues however their role in the folding and misfolding of α(1)-Antitrypsin has never been examined. We have therefore created a range of α(1)Antitypsin variants in order to explore the role of these conserved residues in serpin folding, misfolding, stability and function. Our data suggest that key residues in helix I mediate efficient folding from the folding intermediate and residues in strand 5A ensure native state stability in order to prevent misfolding. Additionally, our data indicate that helix I is involved in the inhibitory process and that both structural elements undergo differing conformational rearrangements during unfolding and misfolding. These findings suggest that the ability of α(1)-Antitrypsin to adopt different types of polymers under different denaturing conditions may be due to subtle conformational differences in the transiently populated structures adopted prior to the I and M* states.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Kinetics
  • Models, Molecular
  • Mutation
  • Protein Conformation
  • Protein Folding*
  • Protein Interaction Domains and Motifs* / genetics
  • Protein Multimerization
  • Protein Stability
  • Thermodynamics
  • alpha 1-Antitrypsin / chemistry*
  • alpha 1-Antitrypsin / genetics
  • alpha 1-Antitrypsin / metabolism

Substances

  • alpha 1-Antitrypsin

Grants and funding

This project was supported by a NHMRC National Health and Medical Research Council Program Grant, a PRF fellowship from the NHMRC to SPB, and an Postdoctoral Fellowship from the AlphaOne Foundation to MCP. The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.