As a member of the ABC superfamily, STE6 is unique in that it has a well-characterized substrate, a-factor, and can be easily manipulated in the yeast system. Functional assays have been extensively used, and methods to examine trafficking and stability of STE6 are well established. In addition, STE6 chimeras and ste6 deletion strains are useful for the analysis of many nonyeast ABC proteins. Continuing studies of STE6 are expected to aid in the identification of novel cellular components involved in the trafficking and functioning of not only STE6, but of other members of the ABC superfamily as well.