A One-Step Staining Probe for Phosphatidylethanolamine.

Phosphatidylethanolamine (PE) is an abundant phospholipid in cellular membranes, but relatively little is known about the kinetics of PE in biological membrane systems. Characterizing PE on a cellular level has been challenging owing to a lack of proper molecular tools. The lantibiotic duramycin and its structural analogue, cinnamycin, are currently the only known polypeptides that have an established stereospecific structure for binding membrane PE with high affinity and high specificity. These lantibiotics are recognized for their potential as molecular probes for studying PE kinetics in various membranes. However, owing to their antibiotic nature, duramycin and cinnamycin exhibit appreciable levels of cytotoxicity at low micromolar concentrations in cultured mammalian cells by inducing membrane distortion and possible PE redistribution. These issues can potentially complicate study design and data interpretation. Here, we report the construction of a molecular probe consisting of duramycin attached to the C terminus of green fluorescent protein (GFP) by a PEG linker at a stoichiometry of 1. The construct retained specific binding toward PE and essentially no cytotoxicity compared to native duramycin. The biological utilities of this probe were demonstrated in a number of cellular staining studies involving PE dynamics. The availability of a one-step, nontoxic molecular probe for PE will enable characterization of the biology of this important phospholipid.