Nature Struct. Bio. Vol. 4, 548-552 (1997)

Protein Alchemy:

Change b-Sheet into a-Helix

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b-sfeet protein - a) B1 domain of IgG-bindinf protein G

• 56 amino acids

a-Helical protein - b) Rop, homodimeric four-helix bundle protein

• 63 amino acids - 7 unstructured amino acids = 56 AAs

Transformation - B1 domain to Rop

The hybrid protein - Janus

- after the Roman god of new beginnings, who bears two faces

• De Novo designed protein share 50% sequence identity with B1 domain but same structural fold with Rop.
• 41% identity with Rop.

Design Strategy

• keep residues with high a-helix forming propensities
• replace residues with high b-sheet forming propensities
• hydrophobic residues put in "a" and "d" positions of a heptad repeat to form the core
• build model - assessed both visually and by energy minimization calculations

Structural characterizations