Royal jelly (RJ) is an exclusive food for queen honey bee (Apis mellifera L.) that is synthesized and secreted by young worker bees. RJ is also widely used in medical products, cosmetics, and as health foods. However, little is known about RJ functionality and the total protein components, although recent research is attempting to unravel the RJ proteome. We have embarked on a detailed investigation of the RJ proteome, using a modified protein extraction protocol and two complementary proteomics approaches, one- and two-dimensional gel electrophoresis (1-DGE and 2-DGE) in conjunction with tandem mass spectrometry. Simultaneously, we examined total soluble protein from RJ collected at 24, 48, and 72 h after honey bee larvae deposition twice (in two flower blooming seasons), to check differences, if any, in RJ proteome therein. Both 1- and 2-D gels stained with silver nitrate revealed similar protein profiles among these three time points. However, we observed a clear difference in two bands (ca. MW of 55 and 75 kDa) on 1-D gel between the first and the second collection of RJ. A similar difference was also observed in the 2-D gel. Except for this difference, the protein profiles were similar at the 3 time points. As the RJ from 48 (or sometimes 72) is commercially used, we selected the RJ sample at 48 h for detailed analysis with the first collection. 1-DGE identified 90 and 15 proteins from the first and second selection, respectively; in total, 47 nonredundant proteins were identified. 2-DGE identified 105 proteins comprising 14 nonredundant proteins. In total, 52 nonredundant proteins were identified in this study, and other than the major royal jelly protein family and some other previously identified proteins, 42 novel proteins were identified. Furthermore, we also report potentially post-translationally modified (phosphorylation and glycosylation) RJ proteins based on the Pro-Q diamond/emerald phosphoprotein/glycoprotein gel stains; MRJP 2p and 7p were suggested as potential phosphoproteins. The 2-DGE data were integrated to develop a 2-D gel reference map, and all data are accessible through RJ proteomics portal (http://foodfunc.agr.ibaraki.ac.jp/RJP.html).

Apisin, a protein that is unique to royal jelly (RJ), is known to compose the greater part of the RJ proteins and to exist as a heterooligomer containing major royal jelly protein 1 and apisimin. However, few reports on the methods for quantifying apisin have been published. Thus, we attempted to quantify apisin using HPLC, a widely used analytical technique, as described below. Isoelectric precipitation and size-exclusion chromatography were used to obtain the purified protein, which was identified as apisin by SDS-PAGE and LC-MS analyses. The purified apisin was lyophilized and then used to generate a calibration curve to quantify apisin in RJ. The apisin content was fairly constant (i.e., 3.93 to 4.67 w/w%) in natural RJ. This study is the first to describe a simple, standardized method for quantifying apisin using HPLC and suggests that apisin can be used as a benchmark for future evaluations of RJ quality.

Manduca sexta is an excellent insect model for studying insect physiology, including hemolymph proteins. Larvae stages of this insect are highly damaging to tobacco leaves causing a drastic decrease in crop yield. Investigation on the larval biology should help in controlling its destructive potential, thus increasing crop yields. The hemolymph is the source of its immunity to disease and environmental factors, which invariably involves protein components. To better understand the physiology of M. sexta and the protein components expressed during its life cycle, two complementary proteomics approaches, one- and two-dimensional gel electrophoresis (1-DGE and 2-DGE) in conjunction with N-terminal amino acid sequencing and liquid chromatography-mass spectrometry, were employed to analyze the fifth instar larvae hemolymph proteins. These proteomics approaches together identified 123 proteins, which constituted a total of 58 nonredundant proteins and belonged to 10 functional categories. Defense (49%), transport and metabolism (15%), storage (9%), and metamorphosis (7%) categories were highly represented accounting for 80% of the identified proteins. Besides identification of previously reported proteins, 18 novel proteins were identified, which include the lipoprotein-releasing system transmembrane protein lolC, 50S ribosomal protein L24, inducible serine protease inhibitor 1, imaginal disk growth factor, protein disulfide-isomerase-like protein ERp57, etc. The 2-DGE data were integrated to develop a 2-D gel reference map. Data obtained from 1-DGE and 2-DGE analyses are accessible through the M. sexta proteomics portal ( http://foodfunc.agr.ibaraki.ac.jp/mansehemoprot.html). Together, this study provides evidence for the presence of a large number of functionally diverse protein families in the hemolymph of M. sexta. These proteins correlate well with the fifth instar stage, the transition from larvae to pupae.