This Article Full Text Full Text (PDF) All Versions of this Article: biophysj.103.032839v1 87/5/3421    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Lear, J. D. Articles by DeGrado, W. F. Search for Related Content PubMed PubMed Citation Articles by Lear, J. D. Articles by DeGrado, W. F.

Association of a Model Transmembrane Peptide Containing Gly in a Heptad Sequence Motif

Department of Biochemistry and Biophysics, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania

Correspondence: Address reprint requests to James D. Lear, Tel.: 215-898-2071; E-mail: lear{at}mail.med.upenn.edu.

A peptide containing glycine at a and d positions of a heptad motif was synthesized to investigate the possibility that membrane-soluble peptides with a Gly-based, left-handed helical packing motif would associate. Based on analytical ultracentrifugation in C14-betaine detergent micelles, the peptide did associate in a monomer-dimer equilibrium, although the association constant was significantly less than that reported for the right-handed dimer of the glycophorin A transmembrane peptide in similar detergents. Fluorescence resonance energy transfer (FRET) experiments conducted on peptides labeled at their N-termini with either tetramethylrhodamine (TMR) or 7-nitrobenz-2-oxa-1,3-diazole (NBD) also indicated association. However, analysis of the FRET data using the usual assumption of complete quenching for NBD-TMR pairs in the dimer could not be quantitatively reconciled with the analytical ultracentrifugation-measured dimerization constant. This led us to develop a general treatment for the association of helices to either parallel or antiparallel structures of any aggregation state. Applying this treatment to the FRET data, constraining the dimerization constant to be within experimental uncertainty of that measured by analytical ultracentrifugation, we found the data could be well described by a monomer-dimer equilibrium with only partial quenching of the dimer, suggesting that the helices are most probably antiparallel. These results also suggest that a left-handed Gly heptad repeat motif can drive membrane helix association, but the affinity is likely to be less strong than the previously reported right-handed motif described for glycophorin A.

This article has been cited by other articles:

				D. Thevenin and T. Lazarova Stable interactions between the transmembrane domains of the adenosine A2A receptor Protein Sci., July 1, 2008; 17(7): 1188 - 1199. [Abstract] [Full Text] [PDF]

				E. Glukhov, M. Stark, L. L. Burrows, and C. M. Deber Basis for Selectivity of Cationic Antimicrobial Peptides for Bacterial Versus Mammalian Membranes J. Biol. Chem., October 7, 2005; 280(40): 33960 - 33967. [Abstract] [Full Text] [PDF]