Autolysin LytA is a protein involved in the virulence of pneumococcus, a pathogenic microorganism in humans. Its C-terminal domain (CLytA) consists of six choline-binding repeats (CBR), arranged in the β-solenoid structure characteristic of choline-binding modules. In the NMR group of the Institute of Physical-Chemistry ‘Rocasolano’ (CSIC) we have structurally characterised a 14-residue peptide encompassing the sequence of the core β-hairpin from the third CBR repeat of CLytA. It has been found that this peptide conserves its native β-hairpin fold in aqueous solution, but forms a stable, amphipathic α-helix (i.e. with two faces, one hydrophobic and the other polar) in detergent micelles (with a hydrophilic surface and a hydrophobic core). These β-hairpin and α-helix structures differ greatly in the distribution of polar hydrophobic side chains. As far as we know, this "chameleonic" behaviour of a micelle-induced structural transition between two ordered peptide structures has not been reported before, and shows the dramatic effect of hydrophobic-hydrophilic interactions. These results could not only be of relevance in the field of peptide design and biosensors, but may also help to understand the molecular basis for the peculiar mechanism of LytA translocation from the cytoplasm to the bacterial surface.
Reference:

Hector Zamora-Carreras, Beatriz Maestro, Erik Strandberg, Anne S. Ulrich, Jesús M. Sanz, y M. Angeles Jiménez. “Micelle-triggered β-hairpin to α-helix transition in a 14-residue peptide derived from the pneumococcal choline-binding protein LytA”. Chemistry-Eur J. 21, 8076-8089 (2015). doi:10.1002/chem.201500447
Enlace a artículos destacados en mayo 2015 por la SBE (http://biofisica.info/zamora-carreras-jimenez-chemistry-21-8076/)