Chameleon peptide

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^[1] and an analysis of Helix-to-Strand Transition Between Peptides with Identical Sequences^[2].

Seeing is believing

To simplify the figure, the entire IgG-Binding domain^[3] is colored . Now, if the amino acids residues, , 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 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.