Optimization of a protein extraction method from natural rubber sheets made of Hevea brasiliensis latex

A method to extract proteins from natural rubber (NR) samples has been developed to characterize the protein composition of NR by SDS-PAGE electrophoresis. While the incubation of NR pieces in aqueous buffers did not provide satisfactory results (no protein bands detected by SDS-PAGE), the solubilization of NR pieces in an organic solvent, prior to centrifugation and protein extraction from the obtained pellet, was found efficient to highlight protein bands by SDS-PAGE. Pure cyclohexane was used to solubilize NR pieces and resulted in a low share of nitrogen in the pellet (29%). The addition of 10% (v/v) ethanol to cyclohexane allowed to significantly increase this share to 73% and to detect 13 protein bands by SDS-PAGE. The molecular weights of the four most intense bands suggest the presence in NR of the following proteins: rubber elongation factor, small rubber particle protein, hevamine, and β-1-3 glucanase.