A majority of the 90 human protein tyrosine kinases (PTKs) are understudied "orphan" enzymes with few or no known substrates. Designing experiments aimed at assaying the catalytic activity of these PTKs has been a long-running problem. In the past, researchers have used polypeptides with a randomized 4:1 molar ratio of glutamic acid to tyrosine as general PTK substrates. However, these substrates are inefficient and perform poorly for many applications. In this work, we apply the KINATEST-ID pipeline for artificial kinase substrate discovery to design a set of candidate "universal" PTK peptide substrate sequences. We identified two unique peptide sequences from this set that had robust activity with a panel of 15 PTKs tested in an initial screen. Kinetic characterization with seven receptor and nonreceptor PTKs confirmed these peptides to be efficient and general PTK substrates. The broad scope of these artificial substrates demonstrates that they should be useful as tools for probing understudied PTK activity.
Bibliographical noteFunding Information:
*E-mail: firstname.lastname@example.org. *E-mail: email@example.com. ORCID Laura J. Marholz: 0000-0002-9269-581X Benjamin E. Turk: 0000-0001-9275-4069 Author Contributions L.J.M. and N.A.Z. contributed equally to this work. Funding This work was supported by the National Institutes of Health (Grants R01CA182543, R33CA183671, and R01GM104047). L.J.M. was supported by a University of Minnesota Cancer Biology Training Grant (T32 CA009138) and a fellowship from the UMN Physical Sciences in Oncology Center grant (U54CA210190). N.A.Z. was supported by a Yale University School of Medicine Cancer Biology Training Grant (T32 CA1932000). Notes The authors declare the following competing financial interest(s): Dr. Laurie Parker owns equity in and serves on the Scientific Advisory Board for KinaSense, LLC. The University of Minnesota and Purdue University review and manage this relationship in accordance with their conflict of interest policies.