Figure 9.

Early small-molecule protein kinase inhibitors of marine origin. (a) A representative protein kinase structure (PDB code 3FJQ) showing a bound peptide inhibitor (orange) and an ATP molecule (purple) plus two Mn²⁺ ions (green spheres) in the crevice that separates the N- and C-terminal lobes. The C-terminal lobe (bottom) contains the activation sites (T196 and phosphorylated T198 in yellow) and substrate-binding site (residues 230–260 in light blue). (b) Chemical structures of two early pan-kinase inhibitors.