Fig. 5: Binding of covalent and non-covalent inhibitors to BTK and effects of amino acid substitutions.

The entire kinase domain-ibrutinib complex structure is in the left-center with ibrutinib in the catalytic site. The N-terminal lobe is in light gray and the C-terminal lobe in dark gray. Side chains are shown for threonine (T) 474, top, and cysteine (C) 481, below, in blue. Top row shows the chemical structures and indicates binding of covalent inhibitors and the bottom row of non-covalent inhibitors. Original residues at positions 474 and 481, T and C, respectively, are in blue. Substitutions at 474 methionine (yellow) and isoleucine (green), at 481 serine (yellow) and threonine (green). For the panels 474 and 481 are indicated in the middle. Ovals in light and dark orange indicate the sites of formation of hydrogen bonds and the covalent bond to cysteine, respectively [36, 41, 47, 50, 51, 60].