In fact, artificial transmembrane domains may have more favorable properties than proteins derived from natural sequences. For example, traptamers can display high specificity, such as the ability to distinguish between human and mouse EPOR. Increased specificity or signaling differences of artificial transmembrane domains compared to natural ligands may reduce harmful side effects,Nedaplatin including those described following administration of high doses of EPO to patients. The utility of these approaches obviously depends on the specificity of traptamers toward a wide range of cellular proteins, which has not yet been assessed, and on the development of methods to properly deliver these agents and regulate their expression or activity. Nevertheless, our results suggest that biologically active transmembrane proteins can serve as templates for new classes of potent peptide or peptidomimetic agents that modulate a wide array of cellular and viral transmembrane proteins. Lipid bilayers form efficient barriers for cellular partitioning. The translocation across these membranous barriers is crucial for many aspects of cell physiology, including the uptake of nutrients,Strontium ranelate the elimination of waste products, or energy generation and cell signaling. The ATP-binding cassette transporters constitute one of the largest families of membrane translocators. The core functional unit of ABC proteins consists of four domains: two cytoplasmic domains containing the highly conserved nucleotidebinding domains, which are responsible for the ATP hydrolysis needed to provide energy for the transport cycle, and two transmembrane domains, each in most cases composed of six membrane-spanning helices, which impart substrate specificity and translocation. The NBDs harbor several conserved sequence motifs from N- to C-terminus. These are the Walker A motif which is glycine-rich, a flexible loop with a conserved glutamine residue, the ABC signature motif, the Walker B motif, and a conserved histidine residue. The ABC signature motif is diagnostic for this family as it is present only in ABC transporters, while Walker A and B motifs are found in many other ATP-utilizing proteins.