title: Subdomain switching reveals regions that harbor substrate specificity and regulatory properties of protein tyrosine kinases.
abstract: Csk and Src are two protein tyrosine kinases that share a similar overall multidomain structural organization and a high degree of sequence homology but have different substrate specificities and regulatory properties. In this study, we generated chimeric kinases of Csk and Src by switching the C-terminal lobes of their catalytic domains, and we characterized their substrate specificity and regulatory properties. First, both Csk and Src phosphorylate Src as a common substrate, but on different Tyr residues. The C-terminal lobes of the kinase catalytic domain determined the site of phosphorylation on Src. Furthermore, toward several physiological substrates of Src, the substrate specificity was also determined by the C-terminal lobe of the catalytic domain regardless of the regulatory domains and the N-terminal lobe of the catalytic domain. Second, Csk and Src represent two general regulatory strategies for protein tyrosine kinases. Csk catalytic domain is inactive and is positively regulated by the regulatory domains, while Src catalytic domain is active and suppressed by its interactions with the regulatory domains. The regulatory properties of the chimeric kinases were more complicated. The regulatory domains and the N-lobe did not fully determine the response to a regulatory ligand, suggesting that the C-lobe also contributes to such responses. On the other hand, the intrinsic kinase activity of the catalytic domain correlates with the identity of the N-lobe. These results demonstrate that the chimeric strategy is useful for detailed dissection of the mechanistic basis of substrate specificity and regulation of protein tyrosine kinases.
authors: Department of Cell and Molecular Biology, University of Rhode Island, Kingston, Rhode Island 02881, USA.
authors: Yue-Hao
authors: YH
authors: Wang
authors: Kezhen
authors: K
authors: Huang
authors: Xiaofeng
authors: X
authors: Lin
authors: Gongqin
authors: G
authors: Sun
mesh_terms: D000818:Animals; D000081247:CSK Tyrosine-Protein Kinase; D020134:Catalytic Domain / Q000235:genetics*; D004789:Enzyme Activation; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D006801:Humans; D050506:Mutant Chimeric Proteins / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D018909:src Homology Domains / Q000235:genetics*; D019061:src-Family Kinases
chemical_list: D050506:Mutant Chimeric Proteins; D011994:Recombinant Proteins; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; C000631346:CSK protein, human