Essenz der Empirischen Chou-Fasman-Regeln:
1. A cluster of four helical residues (Hα or hα) out of six residues along the protein sequence will nucleate a helix, with weak helical residues (Iα) counting as 0.5 hα. The helical segment is extended in both directions until α-tetrapeptide breakers with {Pα} < 1.00 are reached. Pro cannot occur in the inner helix or at the C-terminal helical end. Pro, Asp, Glu and His, Lys, Arg are incorporated, respectively, at the N- and C-terminal ends. Any segment with {Pα} >= 1.03 as well as {Pα} > {Pβ} is predicted as helical.
2. A cluster of three β formers (Hβ or hβ) out of five residues along the protein sequence will nucleate a β-sheet. The β-sheet is extended in both directions until β-tetrapeptide breakers with {Pβ} < 1.00 are reached. Any segment with {Pβ} >= 1.05 as well as {Pβ} > {Pα} is predicted as β-sheet.
3. When regions in proteins contain both α- and β-forming residues, the overlapping region is helical if {Pα} > {Pβ}, or β-sheet if {Pβ} > {Pα}.
4. The probability of bend occurence at residue i is calculated from pt = fi x fi+1 x fi+2 x fi+3 with the aid of a Table of the conformational parameters for β-turn formation. The average probability of β-turn occurence is {pt} = 0.55 x 10-4. Tetrapeptides with pt > 0.75 x 10-4 as well as {Pt} > 1.00 and {Pα} < {Pt} > {Pβ} are selected as probable bends.
Latest update of content: June 12, 2002
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