Soluble protein constituents of the domestic fowl's eggshell

Abstract

1. The protein components of the domestic fowl's eggshell are believed to influence appreciably the mechanical properties of the shell and/or its biomineralisation. The purpose of this study was to compare the protein species composing the eggshell matrix in different parts of the shell structure, by SDS-PAGE and chromatography, utilising eggshell cleaned by different methodologies. 2. Protein species were identified whose absence was associated with the removal of the mammillary knobs. In particular, a prominent 81 kDa protein, as well as 38 and 54 kDa calcium-binding proteins, were concentrated within the mammillary layer, as was a 129 kDa insoluble protein. By contrast, soluble proteins of 54, 33, 22, and 14 kDa were enriched in the palisade layer. 3. Our results demonstrate that the mineralised layers of the fowl's eggshell possess a complex array of distinct proteins. The different proteins which have been detected in the mammillary and palisade layers may be related to the distinct crystallisation patterns of calcium carbonate in these zones of the eggshell.

Protein constituents of the eggshell: eggshell-specific matrix proteins

“…These non-mineral constituents represent about 2% by weight of the calcified eggshell, and can be released for study by demineralization of the eggshell by calcium chelation (EDTA or EGTA) or acid demineralization (acetic acid or HCl), yielding soluble and insoluble constituents. A complex array of distinct protein bands was demonstrated in the soluble intra-and extramineral compartments by 1D-electrophoresis (SDS-PAGE) [18,19], and in the precursor uterine fluid, showing different patterns between the three stages of the eggshell calcification process (initial, growth and terminal) [20]. In contrast, the insoluble components which are not soluble in SDS remain relatively uncharacterized (but see [21,22]).…”

Molecular Cloning and Ultrastructural Localization of the Core Protein of an Eggshell Matrix Proteoglycan, Ovocleidin-116

“…Shell membranes were removed following brief treatment with 1 N HCl at room temperature as described previously (10). Ground shell (140 g) was decalcified in a solution of 0.65 M EDTA, pH 7.5, 10 mM 2-mercaptoethanol, 0.05% NaN 3 .…”

“…1 The proteins are initially secreted by epithelial and glandular cells into the uterine fluid, whose protein composition varies remarkably during the initial, active calcification and terminal phases of eggshell mineralization (9). Sequential deposition of these matrix proteins into the forming eggshell results in their different localization patterns as the inner (mammillary) and outer (palisade) layers of the mineralized shell are assembled (10).…”

Ovocalyxin-32, a Novel Chicken Eggshell Matrix Protein

“…The matrix comprises proteins, glycoproteins, and proteoglycans (3,7,8). Distinct matrix proteins have been identified after decalcification and solubilization of the eggshell extract (9,10). Three of these have previously been identified in the egg white: ovalbumin (11), ovotransferrin (12), and lysozyme (13).…”