Interaction cloning of protein kinase C substrates

We have previously used an overlay assay technique to detect proteins that interact with protein kinase C (PKC) (Hyatt, S. L., Klauck, T., and Jaken, S. (1990) Mol. Carcinogenesis 3, 45-53). In some cases, binding proteins were also identified as substrates. Therefore, we used the overlay assay approach to screen a rat kidney lambda gt11 cDNA library to isolate and identify additional PKC substrates. Two clones have now been characterized. 35A is the rat homologue of the myristoylated alanine-rich C kinase substrate (MARCKS)-related F52 cDNA, whereas 35H is a partial cDNA with substantial homology to the 3' end of beta-adducin. Both cDNAs encode proteins that bind phosphatidyl-serine (PS) and are substrates for PKC. Phosphorylation decreased both PS and PKC binding activities. Both proteins contain high density positive charge domains similar to that found in the major PKC substrate MARCKS. These results demonstrate that PKC interactions with certain substrate proteins are of sufficiently high affinity to facilitate their isolation via interaction cloning.