The functional properties and cellular localization of the human neuronal α7 nicotinic acetylcholine (AcCho) receptor (α7 AcChoR) and its L248T mutated ( mut ) form were investigated by expressing them alone or as gene fusions with the enhanced version of the green fluorescent protein (GFP). Xenopus oocytes injected with wild-type ( wt ), mut α7, or the chimeric subunit cDNAs expressed receptors that gated membrane currents when exposed to AcCho. As already known, AcCho currents generated by wt α7 receptors decay much faster than those elicited by the mut α7 receptors. Unexpectedly, the fusion of GFP to the wt and mutated α7 receptors led to opposite results: the AcCho-current decay of the wt receptors became slower, whereas that of the mutated receptors was accelerated. Furthermore, repetitive applications of AcCho led to a considerable “run-down” of the AcCho currents generated by mut α7-GFP receptors, whereas those of the wt α7-GFP receptors remained stable or increased in amplitude. The AcCho-current run-down of mut α7- GFP oocytes was accompanied by a marked decrease of α-bungarotoxin binding activity. Fluorescence, caused by the chimeric receptors expressed, was seen over the whole oocyte surface but was more intense and abundant in the animal hemisphere, whereas it was much weaker in the vegetal hemisphere. We conclude that fusion of GFP to wt α7 and mut α7 receptors provides powerful tools to study the distribution and function of α7 receptors. We also conclude that fused genes do not necessarily recapitulate all of the properties of the original receptors. This fact must be borne close in mind whenever reporter genes are attached to proteins.