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Structural proteins in the egg-shell of the oriental garden cricket, Gryllus mitratus.

ABSTRACT: 1. The egg-shell of the oriental garden cricket, Gryllus mitratus, contained at least two different types of structural protein in an approximate ratio of 5:1. The major fraction was extracted in a solvent containing dithiothreitol, EDTA and 8m-urea, and was purified to apparent homogeneity as judged by free-boundary electrophoresis and ultracentrifugation. This was designated SH-fraction and its S-carboxymethyl derivative (CM-fraction) was also prepared. The minor fraction, insoluble in the solvent, was designated insoluble residue. 2. The major fraction was a phosphoprotein, rich in serine (29.8mol% of the total amino acids) and phosphate (nearly equimolar to serine), and O-phosphoserine was identified in its partial acid hydrolysate. The content of cystine was rather low (0.9mol%) in spite of the importance of this amino acid residue in the native form of the protein. The insoluble residue contained only a small amount of phosphorus, and its amino acid composition was clearly different from the major fraction. 3. CM-fraction, a fibrous protein with an average molecular weight of 57500, behaved as a typical polyanion owing to the high content of phosphate. SH-fraction and CM-fraction were precipitable from their aqueous solutions by the addition of bivalent metal cations, and the precipitation of CM-fraction by Ca(2+) and Mg(2+) was studied in detail. 4. When SH-fraction was exposed to air, intermolecular disulphide linkages were formed, yielding a net-like gel that changed its volume with changes in Ca(2+), Mg(2+) and Na(+). 5. The possible role of this protein fraction in maintaining the integrity of the egg-shell, and a comparison of its composition and properties with other egg-shell proteins and other phosphoproteins, are discussed.

SUBMITTER: Kawasaki H

PROVIDER: S-EPMC1178084 | biostudies-other | 1971 Nov

REPOSITORIES: biostudies-other

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Project description:BackgroundEggshells which consist largely of calcareous outer shell and shell membranes, constitute a significant part of poultry hatchery waste. The shell membranes (ESM) not only contain proteins that originate from egg whites but also from the developing embryos and different contaminants of microbial and environmental origins. As feed supplements, during post hatch growth, the hatchery egg shell membranes (HESM) have shown potential for imparting resistance of chickens to endotoxin stress and exert positive health effects. Considering that these effects are mediated by the bioactive proteins and peptides present in the membrane, the objective of the study was to identify the protein profiles of hatchery eggshell membranes (HESM).MethodsHatchery egg shell membranes were extracted with acidified methanol and a guanidine hydrochloride buffer then subjected to reduction/alkylation, and trypsin digestion. The methanol extract was additionally analyzed by matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS). The tryptic digests were analyzed by liquid chromatography and tandem mass spectrometry (LC-MS-MS) to identify the proteins.ResultsOur results showed the presence of several proteins that are inherent and abundant in egg white such as, ovalbumin, ovotransferrin, ovocleidin-116, and lysozyme, and several proteins associated with cytoskeletal, cell signaling, antimicrobial, and catalytic functions involving carbohydrate, nucleic acid, and protein metabolisms. There were some blood derived proteins most likely originating from the embryos and several other proteins identified with different aerobic, anaerobic, gram positive, gram negative, soil, and marine bacterial species some commensals and others zoonotic.ConclusionThe variety of bioactive proteins, particularly the cell signaling and enzymatic proteins along with the diverse microbial proteins, make the HESM suitable for nutritional and biological application to improve post hatch immunity of poultry.

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Structural proteins in the egg-shell of the oriental garden cricket, Gryllus mitratus.

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