A polar, solvent-exposed residue can be essential for native protein structure. Structure 2000 May 15;8(5):471-9
Date
05/10/2000Pubmed ID
10801493Pubmed Central ID
PMC3050062DOI
10.1016/s0969-2126(00)00130-1Scopus ID
2-s2.0-0034657321 (requires institutional sign-in at Scopus site) 38 CitationsAbstract
BACKGROUND: A large energy gap between the native state and the non-native folded states is required for folding into a unique three-dimensional structure. The features that define this energy gap are not well understood, but can be addressed using de novo protein design. Previously, alpha(2)D, a dimeric four-helix bundle, was designed and shown to adopt a native-like conformation. The high-resolution solution structure revealed that this protein adopted a bisecting U motif. Glu7, a solvent-exposed residue that adopts many conformations in solution, might be involved in defining the unique three-dimensional structure of alpha(2)D.
RESULTS: A variety of hydrophobic and polar residues were substituted for Glu7 and the dynamic and thermodynamic properties of the resulting proteins were characterized by analytical ultracentrifugation, circular dichroism spectroscopy, and nuclear magnetic resonance spectroscopy. The majority of substitutions at this solvent-exposed position had little affect on the ability to fold into a dimeric four-helix bundle. The ability to adopt a unique conformation, however, was profoundly modulated by the residue at this position despite the similar free energies of folding of each variant.
CONCLUSIONS: Although Glu7 is not involved directly in stabilizing the native state of alpha(2)D, it is involved indirectly in specifying the observed fold by modulating the energy gap between the native state and the non-native folded states. These results provide experimental support for hypothetical models arising from lattice simulations of protein folding, and underscore the importance of polar interfacial residues in defining the native conformations of proteins.
Author List
Hill RB, DeGrado WFMESH terms used to index this publication - Major topics in bold
DimerizationMagnetic Resonance Spectroscopy
Models, Molecular
Mutagenesis, Site-Directed
Peptides
Protein Engineering
Protein Folding
Protein Structure, Tertiary
Solvents
Thermodynamics