Tests for helix-stabilizing interactions between various nonpolar side chains in alanine-based peptides.
Straight-chain, non-natural, nonpolar amino acids norleucine, norvaline, and alpha-amino-n-butyric acid at various spacings do not interact with themselves to stabilize helix formation in alanine-based peptides, but do interact with a Tyr spaced i, i + 4 to stabilize alanine helices, similar to the helix-stabilizing i, i + 4 Tyr-Leu and Tyr-Val interactions reported earlier (Padmanabhan S, Baldwin RL, 1994, J Mol Biol 241:706-713). Leu spaced i, i + 4 from another Leu is measurably helix-stabilizing relative to the corresponding i, i + 3 pair, but less so than for i, i + 4 Val-Leu, Ile-Leu, or Phe-Leu pairs (relative to the corresponding i, i + 3 pairs) when Leu is C-terminal to the other nonpolar amino acid. Our results indicate that limited side-chain flexibility in an alpha-helix strongly favors the interaction between 2 nonpolar residues to stabilize an isolated alpha-helix.
Padmanabhan
S
S
Department of Biochemistry, Beckman Center, Stanford University Medical School, California 94305-5307.
Baldwin
R L
RL
D000409:Alanine / Q000737:chemistry; D000595:Amino Acid Sequence; D000613:Aminobutyrates / Q000737:chemistry; D002942:Circular Dichroism; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D009646:Norleucine / Q000737:chemistry; D010455:Peptides / Q000737:chemistry*; D017510:Protein Folding; D017433:Protein Structure, Secondary; D014633:Valine / Q000031:analogs & derivatives / Q000737:chemistry
D000613:Aminobutyrates; D010455:Peptides; D009646:Norleucine; C005313:norvaline; D014633:Valine; D000409:Alanine