The 3D protein-backbone structure of the β5 subunit of proteasome. The 3D model of protein-backbone structure of the β5 subunit of proteasome (PSMB5) consults the yeast proteasomal crystal structure in complex with bortezomib ; the bovine proteasomal crystal structure ; models made by Franke et al ,. de Wilt et al . and Suzuki et al . Mutation sites are depicted in red. P1, substrate side chain 1; S1, specificity binding pocket 1.