Investigation of Structure Function Relationships in Cathepsin B

Previous suggestions from sequence alignment studies and examination of the recently determined X-ray crystal structures of cathepsin B point to roles for several specific residues in substrate binding and catalysis. The role of these groups is being examined by studying cathepsin B mutants produced using a yeast expression system. The substitutions Gly198Asp, Arg202Ala, His111Gln and Glu245Gln provide a mechanistic basis for the exopeptidase activity of cathepsin B and the ability of this cysteine proteinase to accept an arginine residue in the S2 subsite.