A Novel Reversibly Glycosylated Polypeptide-2 of Bee Pollen from Rape (Brassica napus L.): Purification and Characterization

Background: Reversibly glycosylated polypeptide (RGP), a kind of hydrosoluble and plasmodesmal-associated protein found in plants, plays a crucial role in the development of pollen. Objective: A novel RGP 2 was isolated and identified from rape (Brassica napus L.) bee pollen. Method: RGP2 was isolated and purified by ion-exchange column and gel filtration chromatography, and characterized by MALDI-TOF-MS, LC-MS, immunological histological chemistry, and transmission electron microscope. Results: Our results indicated that the RGP2 is an acidic protein (pI=5.46) with the molecular weight 42388 Da. It contained 17 kinds of amino acids, among which aspartic acid had the highest amount (71.56 mg/g). Homologous alignment of amino acid sequence results showed that RGP2 was 80.33%, 85.02%, 86.06%, and 88.93% identical to Arabidopsis thaliana RGP2 (AtRGP2), Oryza sativa RGP (OsRGP), Triticum aestivum RGP (TaRGP), and Zea maize RGP (ZmRGP), respectively. The localization results showed that RGP2 in rape anther existed in exine and intine of anther cells of rape flower by immunological histological chemistry and the subcellular localization identified that RGP2 appeared around the Golgi apparatus in cytoplasm by transmission electron microscope. Conclusion: RGP2 has a highly conserved sequence of amino acid residues and potential glycosylation sites.