Human epididymis protein-4 (HE-4): a novel cross-class protease inhibitor

PLoS One. 2012;7(11):e47672. doi: 10.1371/journal.pone.0047672. Epub 2012 Nov 5.


Epididymal proteins represent the factors necessary for maturation of sperm and play a crucial role in sperm maturation. HE-4, an epididymal protein, is a member of whey acidic protein four-disulfide core (WFDC) family with no known function. A WFDC protein has a conserved WFDC domain of 50 amino acids with eight conserved cystine residue. HE-4 is a 124 amino acid long polypeptide with two WFDC domains. Here, we show that HE-4 is secreted in the human seminal fluid as a disulfide-bonded homo-trimer and is a cross-class protease inhibitor inhibits some of the serine, aspartyl and cysteine proteases tested using hemoglobin as a substrate. Using SPR we have also observed that HE-4 shows a significant binding with all these proteases. Disulfide linkages are essential for this activity. Moreover, HE-4 is N-glycosylated and highly stable on a wide range of pH and temperature. Taken together this suggests that HE-4 is a cross-class protease inhibitor which might confer protection against microbial virulence factors of proteolytic nature.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chromatography, Affinity
  • Chromatography, Gel
  • Chromatography, Ion Exchange
  • Chromatography, Liquid
  • Glycosylation
  • Humans
  • Male
  • Mass Spectrometry
  • Native Polyacrylamide Gel Electrophoresis
  • Peptides / chemistry
  • Peptides / metabolism
  • Protease Inhibitors / chemistry
  • Protease Inhibitors / isolation & purification
  • Protease Inhibitors / metabolism*
  • Protein Binding
  • Protein Multimerization
  • Proteins / chemistry
  • Proteins / isolation & purification
  • Proteins / metabolism*
  • Semen / metabolism
  • Sequence Analysis, Protein
  • Surface Plasmon Resonance
  • WAP Four-Disulfide Core Domain Protein 2


  • Peptides
  • Protease Inhibitors
  • Proteins
  • WAP Four-Disulfide Core Domain Protein 2
  • WFDC2 protein, human

Grant support

This work was supported by financial grants from the Department of Science and Technology (DST), Government of India. The authors thank the Council of Scientific and Industrial Research (CSIR), New Delhi for the fellowship granted to NC. The authors also thank Department of Science and Technology (DST), Government of India, for providing fellowship to AK. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.