Protein Engineering vol. 16 no. 12 pp. 875-879, 2003
© 2003 Oxford University Press
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A backbone-reversed all-ß polypeptide (retro-CspA) folds and assembles into amyloid nanofibres
Institute of Microbial Technology, Sector 39-A, Chandigarh, India
1 To whom correspondence should be addressed. e-mail: pg{at}imtech.res.in
The backbone-reversed or ‘retro’, form of a model all-ß-sheet protein, Escherichia coli CspA, was produced from a synthetic gene in E.coli in fusion with an N-terminal affinity tag. Following purification under denaturing conditions and dialysis-based removal of urea, the protein was found to fold into a soluble, poorly structured multimer. Upon concentration, this state readily transformed into amyloid nanofibres. Congo Red-binding amorphous forms were also observed. Since a ß-sheet-forming sequence is expected to retain high ß-sheet-forming propensity even after backbone reversal and given the fact that folding of retro-CspA occurs only to a poorly structured form, we conclude that the increase effected in protein concentration may be responsible for the formation of intermolecular ß-sheets, facilitating the bleeding away of the protein’s conformational equilibrium into aggregates that generate well-formed fibres. Since every molecule in these fibres contains a peptide tag for binding Ni2+, the fibres may provide a template for deposition of nickel to generate novel materials.
Received April 1, 2003; revised October 27, 2003; accepted October 30, 2003