Probing the lower size limit for protein-like fold stability: ten-residue microproteins with specific, rigid structures in water.
Mutational optimization of two long-range interactions first observed in Ac-WINGKWT-NH2, (a) bifurcated H-bonding involving the threonine amide H(N) and side chain OH and the N-terminal acetyl carbonyl and (b) an H-bond between the entgegen-H(N) of the C-terminal amide and the indole ring of Trp6 that stabilizes a face-to-edge indole/indole interaction between Trp1 and Trp6, has afforded < or = 10 residue systems that yield a remarkably stable fold in water. Optimization was achieved by designing a hydrophobic cluster that sequesters these H-bonds from solvent exposure. The structures and extent of amide H/D exchange protection for CH3CH2CO-WI pGXWTGPS (p = D-Pro, X = Leu or Ile) were determined. These two systems are greater than 94% folded at 298 K (97.5% at 280 K) with melting temperatures > 75 degrees C. The fold appears to display minimal fluxionality; a well-converged NMR structure rationalizes all of the large structuring shifts observed, and we suggest that these designed constructs can be viewed as microproteins.
Kier
Brandon L
BL
Department of Chemistry, University of Washington, Seattle, Washington 98195, USA.
Andersen
Niels H
NH
D003903:Deuterium; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D009842:Oligopeptides / Q000737:chemistry*; D017510:Protein Folding; D013329:Structure-Activity Relationship; D013696:Temperature; D014867:Water / Q000737:chemistry*
D009842:Oligopeptides; D014867:Water; D003903:Deuterium