Myelin Basic Protein (MHP4-14) TFA, a synthetic peptide comprising residues 4-14 of myelin basic protein, is a very selective PKC substrate (Km=7 μM). Myelin Basic Protein TFA is not phosphorylated by cyclic AMP-dependent protein kinase, casein kinases I and II, Ca2+/calmodulin-dependent protein kinase II, or phosphorylase kinase, and can be routinely used for the assay of protein kinase C with low background in the crude tissue extracts.