Chameleon peptide

Does the amino acid sequence really determine the 3D structure of a peptide?

spinqualitylabelsall models Protein G immunoglobulin binding domain (PDB code 2gb1) Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Chamelion General question To determine the extent to which non-local factors influence the formation of secondary structural elements Methodology Design the longest possible sequence that can fold into an alpha-helix when inserted into one place in a protein sequence and a beta-sheet when inserted into another. Two key references are: on a Chameleon peptide and an analysis of Helix-to-Strand Transition Between Peptides with Identical Sequences. Seeing is believing To simplify the figure, the entire IgG-Binding domain is colored beige. Now, if the amino acids residues, <23-33>, are changed to the Chameleon sequence i.e. AWTVEKAFKTF, virtually no change in structure is seen. Specifically the WT sequence in yellow (residues 23-33) is changed to Chameleon sequence shown in pink, , n.b. only 5 AA's have been changed in this region WT:      TTYKLILNGKTLKGETTTEAVDAATAEKVFKQYANDNGVDGEWTYDDATKTFTVTEK Mutated: TTYKLILNGKTLKGETTTEAVDAWTVEKAFKTFANDNGVDGEWTYDDATKTFTVTEK If a similar change in the WT sequences is made to the Chameleon sequence for residues 42-52 again virtually no change in the 3D structure of this protein is seen. WT:      TTYKLILNGKTLKGETTTEAVDAATAEKVFKQYANDNGVDGEWTYDDATKTFTVTEK Mutated: TTYKLILNGKTLKGETTTEAVDAATAEKVFKQYANDNGVDGAWTVEKAFKTFTVTEK 3D structure of a sequence adopts to its environment The 3D structure of the Chameleon sequence, AWTVEKAFKTF, appears to adopt to its environment.

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