Molecular and immunochemical characterization of Pop n 2: A new allergen of Populus nigra pollen

Clin Exp Allergy. 2021 Dec;51(12):1613-1623. doi: 10.1111/cea.13789. Epub 2021 Jan 26.


Background: Pollen is one of the most common allergens that cause respiratory allergies worldwide. Pollen grains from poplars have been reported as important sources of pollinosis in many countries.

Objective: The aim of the present study was to determine the molecular and immunochemical characterization of Pop n 2, a novel allergen of Populus nigra (P nigra) pollen extract.

Methods: In this study, the pollen extract of P nigra was analysed by SDS-PAGE, and the allergenic profile was determined by IgE immunoblotting and specific ELISA using the sera of twenty allergic patients. The coding sequence of Pop n 2 was cloned and expressed in the Escherichia coli BL21 (DE3) using plasmid the pET-21b (+). Finally, the expressed recombinant Pop n 2 was purified by affinity chromatography.

Results: Pop n 2 belongs to the profilin family with a molecular weight of approximately 14 kDa. Pop n 2 is the most IgE-reactive protein (about 65%) in the P nigra pollen extract. The cDNA sequencing results indicated an open reading frame 396 bp that encodes 131 amino acid residues. The results of ELISA and Immunoblotting assays showed that recombinant Pop n 2 could react with the IgE antibody in patients' sera, like its natural counterpart.

Conclusion: Our data revealed that Pop n 2 is a significant allergen in the P nigra pollen extract. Moreover, we observed that the recombinant Pop n 2 produced by the pET-21b (+) vector in the E colisystem acts as its natural counterpart.

Keywords: Populus nigra; Pop n 2; allergen; characterization; profilin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Allergens
  • Amino Acid Sequence
  • Cloning, Molecular
  • Cross Reactions
  • Humans
  • Immunoglobulin E
  • Plant Proteins / genetics
  • Pollen
  • Populus* / genetics
  • Populus* / metabolism
  • Recombinant Proteins


  • Allergens
  • Plant Proteins
  • Recombinant Proteins
  • Immunoglobulin E