W0191

Understanding Oncogenic Mutations in the Tyrosine Kinase Domain of Met: Modeling Studies. Maria Miller, Macromolecular Structure Laboratory, ABL-BRP, NCI-FCRDC, Frederick, MD 21702, Krzysztof Ginalski, ICM, University of Warsaw, Warsaw, Poland

The Met proto-oncogene encodes a cell membrane receptor tyrosine kinase which upon activation by its ligand mediates cell growth, differentiation and migration in several tissues. Recently, mutations responsible for hereditary and sporadic cases of renal papillary carcinoma were located in the kinase domain of Met [Schmidt, L., et al.; 1997, Nat.Genet. 16, 68-73]. As demonstrated in biochemical and biological assays, these mutations increase the level of tyrosine autophosphorylation and enzymatic activity toward exogenous substrates of wild-type Met and some mutants exhibit transforming ability [Jeffers, M., et al.; 1997, Proc.Natl.Acad.Sci USA, 94, 11445-11450]. In order to elucidate the mechanism of action of mutated Met proteins, we constructed several models of the wild-type and mutated Met catalytic core kinase domain. Ligand-independent activation of Met can best be explained by the model based on the crystal structure of the tyrosine kinase domain of the human insulin receptor in its inactive "open" form (PDB code: 1IRK). The transforming potential of mutations which could be attributed to a change in the substrate specificity [Nakaigawa, N., to be published] will be discussed based on the modeled complexes of wild-type Met with its natural substrates and highly activating M1268T mutant with the optimal substrate for c-Abl cytoplasmic tyrosine kinase.

Research sponsored in part by the National Cancer Institute, DHHS, under contract with ABL.