Alvaro I. Herrera, Ahlam Al-Rawi, and Gabriel A. Cook contributed equally to this work.
Structural characterization of two pore-forming peptides: Consequences of introducing a C-terminal tryptophan
Article first published online: 31 MAR 2010
Copyright © 2010 Wiley-Liss, Inc.
Proteins: Structure, Function, and Bioinformatics
Volume 78, Issue 10, pages 2238–2250, 1 August 2010
How to Cite
Herrera, A. I., Al-Rawi, A., Cook, G. A., Gao, J., Iwamoto, T., Prakash, O., Tomich, J. M. and Chen, J. (2010), Structural characterization of two pore-forming peptides: Consequences of introducing a C-terminal tryptophan. Proteins, 78: 2238–2250. doi: 10.1002/prot.22736
- Issue published online: 7 JUN 2010
- Article first published online: 31 MAR 2010
- Accepted manuscript online: 31 MAR 2010 12:00AM EST
- Manuscript Accepted: 17 MAR 2010
- Manuscript Revised: 9 MAR 2010
- Manuscript Received: 29 DEC 2009
- National Institutes of Health. Grant Numbers: GM 074096, P20 RR017686
- anion selectivity;
- molecular dynamics;
- molecular modeling;
- ion channel;
- solution NMR;
- structure refinement;
- synthetic channel
Synthetic channel-forming peptides that can restore chloride conductance across epithelial membranes could provide a novel treatment of channelopathies such as cystic fibrosis. Among a series of 22-residue peptides derived from the second transmembrane segment of the glycine receptor α1-subunit (M2GlyR), p22-S22W (KKKKP ARVGL GITTV LTMTT QW) is particularly promising with robust membrane insertion and assembly. The concentration to reach one-half maximal short circuit current is reduced to 45 ± 6 μM from that of 210 ± 70 μM of peptide p22 (KKKKP ARVGL GITTV LTMTT QS). However, this is accompanied with nearly 50% reduction in conductance. Toward obtaining a molecular level understanding of the channel activities, we combine information from solution NMR, existing biophysical data, and molecular modeling to construct atomistic models of the putative pentameric channels of p22 and p22-S22W. Simulations in membrane bilayers demonstrate that these structural models, even though highly flexible, are stable and remain adequately open for ion conductance. The membrane-anchoring tryptophan residues not only rigidify the whole channel, suggesting increased stability, but also lead to global changes in the pore profile. Specifically, the p22-S22W pore has a smaller opening on average, consistent with lower measured conductance. Direct observation of several incidences of chloride transport suggests several qualitative features of how these channels might selectively conduct anions. The current study thus helps to rationalize the functional consequences of introducing a single C-terminal tryptophan. Availability of these structural models also paves the way for future work to rationally modify and improve M2GlyR-derived peptides toward potential peptide-based channel replacement therapy. Proteins 2010. © 2010 Wiley-Liss, Inc.