Investigation of structure function relationships in cathepsin B

Area of Science:

• Biochemistry
• Enzymology
• Molecular Biology

Background:

• Sequence alignment and X-ray crystallography suggest specific residues in cathepsin B are crucial for substrate binding and catalysis.
• Understanding these residues' roles is key to elucidating cathepsin B's function.

Purpose of the Study:

• To investigate the functional roles of specific cathepsin B residues in substrate binding and catalysis.
• To provide a mechanistic basis for cathepsin B's exopeptidase activity and its substrate specificity.

Main Methods:

• Utilized a yeast expression system to generate cathepsin B mutants.
• Introduced specific amino acid substitutions: Gly198Asp, Arg202Ala, His111Gln, and Glu245Gln.

Main Results:

• Mutant analysis provided insights into the catalytic mechanism of cathepsin B.
• Demonstrated a mechanistic basis for the exopeptidase activity of cathepsin B.
• Showed that cathepsin B can accept an arginine residue in the S2 subsite, influenced by the studied mutations.

Conclusions:

• The examined mutations (Gly198Asp, Arg202Ala, His111Gln, Glu245Gln) elucidate the roles of specific residues in cathepsin B function.
• These findings offer a mechanistic explanation for cathepsin B's exopeptidase activity and its interaction with arginine residues.