Functional refolding of a recombinant C-type lectin-like domain containing intramolecular disulfide bonds

Protein Expr Purif. 2007 Apr;52(2):415-21. doi: 10.1016/j.pep.2006.11.012. Epub 2006 Dec 1.

Abstract

The lectin-like oxidized low-density lipoprotein scavenger receptor (LOX-1) is a pro-inflammatory marker and Type II membrane protein expressed on vascular cells and tissues. The LOX-1 extracellular domain mediates recognition of oxidized low-density lipoprotein (oxLDL) particles that are implicated in the development of atherosclerotic plaques. To study the molecular basis for LOX-1-mediated ligand recognition, we have expressed, purified and refolded a recombinant LOX-1 protein and assayed for its biological activity using a novel fluorescence-based assay to monitor binding to lipid particles. Overexpression of a hexahistidine-tagged cysteine-rich LOX-1 extracellular domain in bacteria leads to the formation of aggregates that accumulated in bacterial inclusion bodies. The hexahistidine-tagged LOX-1 molecule was purified by affinity chromatography from solubilized inclusion bodies. A sequential dialysis procedure was used to refold the purified but inactive and denatured LOX-1 protein into a functionally active form that mediated recognition of oxLDL particles. This approach allowed slow LOX-1 refolding and assembly of correct intrachain disulfide bonds. Circular dichroism analysis of the refolded LOX-1 molecule demonstrated a folded state with substantial alpha-helical content. Using immobilized recombinant, refolded LOX-1 we demonstrated a 70-fold preferential recognition for oxLDL over native LDL particles. Thus, a protein domain containing intrachain disulfide bonds can be reconstituted into a functionally active state using a relatively simple dialysis-based technique.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Disulfides / chemistry*
  • Lipoproteins, LDL / metabolism*
  • Oxidation-Reduction
  • Protein Denaturation
  • Protein Folding
  • Protein Structure, Tertiary
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Scavenger Receptors, Class E / chemistry
  • Scavenger Receptors, Class E / metabolism*

Substances

  • Disulfides
  • Lipoproteins, LDL
  • OLR1 protein, human
  • Recombinant Proteins
  • Scavenger Receptors, Class E
  • oxidized low density lipoprotein