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Contribution of the HEDJ/ERdj3 cysteine-rich domain to substrate interactions

Nancy Y Marcus1, Roland A Marcus, Bela Z Schmidt

  • 1Department of Pediatrics and Molecular Microbiology, Washington University School of Medicine, 660 South Euclid, St. Louis, MO 63110, USA. nmarcus@slu.edu

Archives of Biochemistry and Biophysics
|November 3, 2007
PubMed

Insights

The endoplasmic reticulum chaperone HEDJ (ERdj3) utilizes a unique oxidized Cys-rich domain for substrate binding, unlike cytoplasmic DnaJ/Hsp40 proteins. This oxidation state is crucial for HEDJ

Area of Science:

  • Molecular Biology
  • Protein Biochemistry
  • Cellular Stress Response

Background:

  • Cytoplasmic type I DnaJ/Hsp40 chaperones feature a reduced, zinc-coordinating Cys-rich domain.
  • The endoplasmic reticulum-localized HEDJ (ERdj3) chaperone exhibits distinct structural and redox properties in its Cys-rich region.

Purpose of the Study:

  • To investigate the structural and functional characteristics of the HEDJ Cys-rich domain.
  • To determine the role of the oxidation state of the HEDJ Cys-rich domain in substrate interaction.

Main Methods:

  • Analysis of HEDJ Cys-rich domain sequence and motif arrangement.
  • Assessment of HEDJ binding to denatured thyroglobulin under varying redox conditions.
  • In vitro binding assays using HEDJ mutants with cysteine residues substituted by serine.

Main Results:

  • The HEDJ Cys-rich domain contains predominantly oxidized CXC and CXXC motifs, forming intramolecular disulfide bonds.
  • HEDJ binds to denatured thyroglobulin in its native state, and this interaction is redox-sensitive.
  • Substitution of cysteine residues in the HEDJ Cys-rich domain significantly impairs substrate binding.

Conclusions:

  • The Cys-rich region of HEDJ is predominantly oxidized, differing from cytoplasmic DnaJ/Hsp40 chaperones.
  • The oxidation state of the HEDJ Cys-rich domain is critical for maintaining its substrate-binding competence.
  • These findings highlight a unique redox-dependent mechanism for substrate recognition by ER-localized HEDJ.

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