cDNA cloning of a molecule that restores PAC-1 binding. The mutant cells transiently transfected with a cDNA library were analyzed in PAC-1 binding, and the cells that showed high levels of PAC-1 binding within a window were sorted. Plasmids were rescued from these sorted cells and amplified by E coli into which cDNA plasmids were transformed. After 3 rounds of cDNA transient transfection, cell sorting, and plasmid rescue, finally, 5 cDNA clones that exhibited significant restoration of PAC-1 binding in the mutant cells were isolated.