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.
Department of Chemistry, University of Washington, Seattle, Washington 98195, USA.
Brandon L
BL
Kier
Niels H
NH
Andersen
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