Purification and characteristics of individual major royal jelly protein 1–3

Major royal jelly proteins (MRJPs) are deemed to the most characteristic and abundant constituents in royal jelly. The present paper establishes a sequential process to purify the natural MRJP 1–3 by three different chromatographic procedures. Five individual proteins were obtained, including MRJP 1 oligomer 1, MRJP 1 oligomer 2, MRJP 1 monomer, MRJP 2 and MRJP 3s (contain three MRJP 3 variants) with a purity of 89.88%, 67.79%, 99.92%, 99.41%, and 99.97%, respectively. This is the first report that MRJP 1 mainly possesses three oligomers: a 228 kDa MRJP 1 oligomer 1, a 408 kDa MRJP 1 oligomer 2 and a 639 kDa MRJP 1 oligomer 3. We infer that MRJP 1 oligomer 3 (639 kDa) may be assembled by MRJP 1 oligomer 1 (228 kDa) and MRJP 1 oligomer 2 (408 kDa). The secondary structure of the purified MRJP 1–3 consisted predominantly of β-sheets and random coil in the native conformation. Our results will contribute to the physiological and physicochemical function of the purified individual MRJPs.