MT1 expression yields obtained with ten combinations of cDNA constructs and host systems.

<p>Expression levels of the human MT1 receptor were assessed using a [<sup>3</sup>H]-melatonin ligand binding assay. N: number of independent experiments. Schematic representations of the evaluated expression vectors use the following abbreviations: MT1, human MT1 receptor; His, 10-histidine tag; attB1 and attB2, recombination sites of the Gateway system; Tev, tobacco etch virus protease cleavage site; Trx protein, thioredoxin protein; α-F, sequence signal of the <i>Saccharomyces cerevisiae</i> α-Factor; Flag, flag-epitope tag; Biotin, biotinylation domain from <i>Propionibacterium shermanii</i>; Gαi1, αi1 subunit of G protein; ss, signal sequence from influenza hemagglutinin gene; YFP, yellow fluorescent protein; and 2-Strep, double Strep tag.</p>