2H NMR studies of a myristoylated peptide in neutral and acidic phospholipid bicelles

Deuterium NMR spectra of Myr-d27-GNAAAAKKGSEQES (Cat14), the N-terminal 14-residue peptide from the catalytic subunit of cAMP-dependent protein kinase A (PKA), illustrate how magnetically aligned neutral and acidic phospholipid bicelles can be used to characterize the ordering and mode of binding of peptides to membranes. Since Cat14 is electrically neutral, the major interaction responsible for binding is the insertion of the myristoyl group into the hydrophobic core of the bilayer. The inclusion of 25% phosphatidylserine or phosphatidylglycerol into phosphatidylcholine bicelles results in a moderate increase in the ordering of the peptide relative to the bicelle normal, presumably because of favorable electrostatic interactions between the phospholipid headgroups and the two lysines in positions 7 and 8. Successful preparation of acidic bicelles was achieved by careful adjustment of lipid composition, pH and ionic strength.