Related Experiment Video
Updated: Jul 19, 2026

Exploring Caspase Mutations and Post-Translational Modification by Molecular Modeling Approaches
Published on: October 13, 2022
The crystal structure of a Cys25 -> Ala mutant of human procathepsin S elucidates enzyme-prosequence interactions
Guido Kaulmann1, Gottfried J Palm, Klaus Schilling
1Institut für Biochemie I, Klinikum der Friedrich-Schiller-Universität Jena, D-07740 Jena, Germany.
Abstract:
The crystal structure of the active-site mutant Cys25 --> Ala of glycosylated human procathepsin S is reported. It was determined by molecular replacement and refined to 2.1 Angstrom resolution, with an R-factor of 0.198. The overall structure is very similar to other cathepsin L-like zymogens of the C1A clan. The peptidase unit comprises two globular domains, and a small third domain is formed by the N-terminal part of the prosequence. It is anchored to the prosegment binding loop of the enzyme. Prosegment residues beyond the prodomain dock to the substrate binding cleft in a nonproductive orientation. Structural comparison with published data for mature cathepsin S revealed that procathepsin S residues Phe146, Phe70, and Phe211 adopt different orientations. Being part of the S1' and S2 pockets, they may contribute to the selectivity of ligand binding. Regarding the prosequence, length, orientation and anchoring of helix alpha3p differ from related zymogens, thereby possibly contributing to the specificity of propeptide-enzyme interaction in the papain family. The discussion focuses on the functional importance of the most conserved residues in the prosequence for structural integrity, inhibition and folding assistance, considering scanning mutagenesis data published for procathepsin S and for its isolated propeptide.
More Related Videos
09:31PCR Mutagenesis, Cloning, Expression, Fast Protein Purification Protocols and Crystallization of the Wild Type and Mutant Forms of Tryptophan Synthase
Published on: September 26, 2020
19:16The Importance of Correct Protein Concentration for Kinetics and Affinity Determination in Structure-function Analysis
Published on: March 17, 2010
Related Concept Videos
Protein Folding
Protein Structure Is Critical to Its Biological Function
Proteins perform a wide range of biological functions such as catalyzing chemical reactions, providing...
Protein Folding
Allosteric Proteins-ATCase
Aspartate transcarbamoylase (ATCase) is a cytosolic enzyme that catalyzes the condensation of L-aspartate and carbamoyl phosphate to N-carbamoyl-L-aspartate. This reaction is the first step in pyrimidine biosynthesis. UTP and CTP, the end products of the pyrimidine synthesis pathway,...
Protein Organization
The primary structure of a protein is its amino acid sequence.
The Proteasome Structure
The proteasome is an...
Protein and Protein Structure
A protein's shape is critical to its function. For example, an enzyme can...