Proteomics of arabinogalactan-proteins

French National Research Institute for Agriculture, Food and Environment (INRAE)

Organisation/Company French National Research Institute for Agriculture, Food and Environment (INRAE) Department Transform Research Field Biological sciences » Biological engineering Researcher Profile First Stage Researcher (R1) Positions Postdoc Positions Application Deadline 1 Dec 2026 - 00:00 (Europe/Paris) Country France Type of Contract Temporary Job Status Full-time Hours Per Week 35 Offer Starting Date 1 Nov 2026 Is the job funded through the EU Research Framework Programme? Not funded by a EU programme Is the Job related to staff position within a Research Infrastructure? No

Offer Description

1. Objectives.Acacia gums are very interesting hydrocolloids used for stabilizing dispersed systems such as emulsions and foams and for coating solid materials due to their excellent adhesive and interfacial properties. These properties would come from the presence of a continuum of molecular species, in particular arabinogalactan-protein and glycoprotein, whose chemical composition and three-dimensional structure promote the adhesion and interaction on solid and liquid interfaces. No work to our knowledge however reports a thorough fundamental understanding of the sequence of proteins linked to polysaccharide blocks of Acacia gum and their three molecular fractions, arabinogalactan-peptide (FI), arabinogalactan-protein or AGP (FII) and glycoprotein (FIII). From literature, deglycosylation by hydrofluoric acid (HF) of Acacia gum revealed two putative core polypeptides (Mahendran et al., 2008) with a molecular mass of approximately 3×104 Da and 5×103 Da. This suggests the presence of two core polypeptides of∼250 and∼45 amino acids, respectively. It seems that a consensus would exist from literature for at least one core polypeptide of 250 amino acids but nobody knows today how many core polypeptides are present in Acacia gums.

2. Previous results.We determined the number of aminoacids in Acacia senegal gum from far-UV circular dichroism data and calculations (Renard et al., Biomacromolecules, 2006). The average number of amino acids residues were of 164, 43, 2253, 4443 for A. senegal gum, FI, FII, FIII, respectively. The number of residues in particular for FIII was considered to be a rough estimation considering the different populations identified by HPSEC-MALLS. The number of aminoacids calculated in FI was in close agreement with the core protein band identified by gel electrophoresis by Mahendran et al. (2008).

We also performed recently preliminary gel electrophoresis in 1D and 2D in order to identify putative protein bands on two gums, A. senegal and A. seyal and FI and FIII molecular fractions. Two major bands were identified for A. senegal and 1 major band for A. seyal.

3. Tasks of the project.The different tasks can be summarized as follows:

• Reproduce 1D and 2D gel electrophoresis on Acacia gums and molecular fraction FIII
• Deglycosylation of Acacia gums (Senegal and Seyal) and molecular fraction FIII by the commercial kit available (Sigma deglycosylation kit protocol) and previously successfully used by Thierry Doco (SPO, Montpellier).
• Gel electrophoresis (SDS-PAGE) of deglycosylated samples
• Protein extraction from gel electrophoresis bands
• Amino-acid analysis (outsourced to Eurofins, Nantes)
• Mass spectrometry to identify the sequence (in collaboration with D. Ropartz and H. Rogniaux, BIBS platform, Nantes)

4. Expected results.Elucidate the sequence of aminoacids of the different core polypeptides attached to the polysaccharide blocks of Acacia gums and molecular fraction FIII. From the knowledge of the core polypeptides, a refined structural arrangement of polysaccharide blocks along the polypeptide backbone could be proposed.

Requirements

Research Field Biological sciences » Biological engineering Education Level PhD or equivalent