Fig. 1.

Folds versus sequences on a lattice. White and black circles denote hydrophobic (H) and polar (P) residues, respectively. Each pattern of H and P circles constitutes a map. For any given map, a fixed sequence (e.g., column 1) can have multiple (or no) conformations which produce the same map (e.g., rows 1 and 2). On the other hand, each conformation (row) has one and only one sequence that can produces any map. For clarity, two-dimensional lattices are depicted; nevertheless, the results mainly pertain to three-dimensional lattices which are descriptive of protein folds.