The Citrus clementina putative allergens: from proteomic analysis to structural features.

Area of Science:

• Allergen identification
• Plant biochemistry
• Immunology

Background:

• Citrus fruits are known sources of allergens, including germin-like proteins (GPLs), profilins, and non-specific lipid transfer proteins (nsLTPs).
• Understanding the specific allergens and their expression in different Citrus species is crucial for managing food allergies.

Purpose of the Study:

• To identify novel putative allergens in Citrus clementina fruit peel.
• To determine the expression levels of these identified allergens.
• To predict the function and structure of a newly identified allergen.

Main Methods:

• In silico sequence analysis to identify potential allergen candidates.
• Protein purification and mass spectrometry (LTQ-Orbitrap XL) for allergen identification.
• Spectral counting method to quantify allergen expression levels.
• Homology modeling using RCSB PDB Database to predict protein structure and function.

Main Results:

• Fifteen new sequences identified as putative germin-like proteins (Cit cl 1) and two as non-specific lipid transfer proteins (Cit cl 3).
• No new profilin sequences (Cit cl 2) were identified.
• Cit cl 1 exhibited a significantly higher expression level in fruit peel compared to Cit cl 2 and Cit cl 3.
• Cit cl 1's primary sequence showed high structural correspondence with barley oxalate oxidase.

Conclusions:

• Citrus clementina possesses novel allergens, particularly GPLs (Cit cl 1) and nsLTPs (Cit cl 3).
• Cit cl 1 is the most abundant allergen identified in the peel.
• The predicted oxalate oxidase-like function of Cit cl 1 warrants further investigation regarding its allergenic potential.