Isoprenylated proteins are involved in signal transduction, control of cell growth and differentiation, organization of the nuclear lamina and cytoskeleton, and vesicle sorting. The isoprenoid moiety facilitates the interaction of these proteins with membranes and/or other proteins. However, many isoprenylated proteins remain unidentified. A method is described for identifying novel and known cDNAs encoding isoprenylated proteins. Sufficient details of the screening procedure are given so that this method may be easily used to identify cDNAs encoding other covalently modified proteins or proteins possessing high affinity ligand binding sites.