MUTATIONAL ANALYSIS OF CONSERVED RESIDUES OF THE BETA-SUBUNIT OF HUMAN FARNESYL-PROTEIN TRANSFERASE

The roles of 11 conserved amino acids of the beta-subunit of human far nesyl:protein transferase (FTase) were examined by performing kinetic and biochemical analyses of site-directed mutants. This biochemical in formation along with the x-ray crystal structure of rat FTase indicate s that residues His-248, Arg-291, Lys-294, and Trp-303 are involved wi th binding and utilization of the sub strate farnesyl diphosphate. Our data confirm structural evidence that amino acids Cys-299, Asp-297, a nd His-362 are ligands for the essential Zn2+ ion and suggest that Asp -359 may also play a role in Zn2+ binding. Additionally, we demonstrat e that Arg-202 is important for binding the essential C-terminal carbo xylate of the protein substrate.