Environment-Dependent Dimerization as a Functional Switch in Leech Cystatin CysHv
Melissa Regina Fessel1, Ana Marisa Chudzinski-Tavassi1,2, Fernanda Faria1
1Laboratory of Development and Innovation, Butantan Institute, Av. Vital Brasil, 1500-Butantã, Sao Paulo 05503-900, Brazil.
Toxins
|July 27, 2026
Summary
The Brazilian leech cystatin CysHv can form inactive dimers, a process influenced by pH and potentially regulated by its conformation. This oligomerization mechanism may control its protease inhibitory activity in different environments.
Area of Science:
- Biochemistry
- Molecular Biology
- Parasitology
Background:
- Cystatins from blood-feeding organisms regulate host proteases.
- CysHv, a cystatin from *Haementeria vizottoi*, inhibits papain and cathepsin L.
- CysHv's inhibitory activity is linked to its conformational state.
Purpose of the Study:
- Investigate the conformational dynamics of CysHv.
- Determine the mechanism of CysHv dimerization.
- Understand how dimerization affects CysHv's inhibitory function.
Main Methods:
- Protein purification and characterization.
- Dimerization assays (time, temperature, concentration dependence).
- Disulfide engineering of a mutant CysHv.
- Comparative structural analysis of cystatins.
Main Results:
- CysHv dimerizes in a time-, temperature-, and concentration-dependent manner, losing inhibitory activity.
- A domain-swapping-like mechanism is proposed, supported by a disulfide-engineered mutant.
- Acidic pH accelerates dimerization kinetics but does not trigger it.
- Structural analysis reveals conserved charged residues in secreted cystatins potentially involved in pH-sensitive dimerization.
Conclusions:
- CysHv is a dimer-prone cystatin whose oligomerization regulates its protease inhibitory activity.
- Dimerization, possibly via a domain-swapping-like mechanism, is influenced by environmental factors like pH.
- Understanding CysHv's conformational plasticity is key to its biotechnological applications.
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