The invention provides parkin binding polypeptides and encoding nucleic acids. The invention also provides antibodies specific for the parkin binding polypeptides. The invention additionally provides methods of detecting a parkin binding polypeptide and detecting a nucleic acid encoding a parkin binding polypeptide. The invention further provides methods of using a parkin binding polypeptide. In one embodiment, the invention provides a method of identifying a candidate drug for treating Parkinson's disease by contacting a parkin binding polypeptide with one or more compounds and identifying a compound that alters the activity of the parkin binding polypeptide.