This volume emphasizes methods for the assay, purification, and characterization of adenylyl cyclases, guanine nucleotide-dependent regulatory proteins (G proteins), and guanylyl cyclases. Key Features * Adenylyl cyclase: determination of activity * Preparation of materials useful in purification of components of hormonally responsive cyclase systems * Purification guanine nucleotide-dependent regulatory proteins * Purification and characterization of g proteins: labeling and quantitating of G proteins * Reconstitution guanylyl cyclase: assay * Preparation of materials used for study of the cyclase * Purification .