Updated project metadata. Ethylene receptor protein quantification is essential to study their functions, but is impaired by low resolutive tools such as antibodies that are mostly nonspecific. Here we report a proteomic method that enables the quantification of all tomato ethylene receptors, which can be applied to other organisms. Testing this method, we found that “Never-Ripe” tomatoes stay orange while a mutated receptor accumulated at ripening, further blocking the ethylene signal .