10.1021/jm980573a.s001 Thomas J. Lukas Thomas J. Lukas Salida Mirzoeva Salida Mirzoeva Urszula Slomczynska Urszula Slomczynska D. Martin Watterson D. Martin Watterson Identification of Novel Classes of Protein Kinase Inhibitors Using Combinatorial Peptide Chemistry Based on Functional Genomics Knowledge American Chemical Society 1999 Novel Classes CaM kinase II myosin light chain kinase reading frame 50 nM activity screens genomics analysis discovery approach autoinhibitory sequences Protein Kinase Inhibitors prototype calmodulin combinatorial peptide library production Combinatorial Peptide Chemistry MLCK Peptide 18 IC 50 protein peptide 18 lack CaM recognition activity signal transduction pathways Functional Genomics Knowledge 1999-02-24 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Identification_of_Novel_Classes_of_Protein_Kinase_Inhibitors_Using_Combinatorial_Peptide_Chemistry_Based_on_Functional_Genomics_Knowledge/3684066 A discovery approach based on an intramolecular inhibitory mechanism was applied to a prototype calmodulin (CaM)-regulated protein kinase in order to demonstrate a proof-of-principle for the development of selective inhibitors. The overall approach used functional genomics analysis of myosin light chain kinase (MLCK) to identify short autoinhibitory sequences that lack CaM recognition activity, followed by recursive combinatorial peptide library production and comparative activity screens. Peptide<b> 18</b> (Arg-Lys-Lys-Tyr-Lys-Tyr-Arg-Arg-Lys-NH<sub>2</sub>), one of several selective inhibitors discovered, has an IC<sub>50</sub> = 50 nM for MLCK, inhibits CaM kinase II only at 4000-fold higher concentrations, and does not inhibit cyclic AMP-dependent protein kinase. Analogues of peptide<b> 18 </b>containing conformationally constrained <i>cis</i>-4-aminocyclohexanecarboxylic acid retained affinity and selectivity. The inhibitors add to the armamentarium available for the deconvolution of complex signal transduction pathways and their relationship to homeostasis and disease, and the approach is potentially applicable to enzymes in which the catalytic and regulatory domains are found within the same open reading frame of a cDNA.