The proteome of the calcified layer organic matrix of turkey (Meleagris gallopavo) eggshell

Abstract

BackgroundChicken eggshell mineralization is a prominent model for biomineralization not only because of its importance for avian reproduction but also because of the commercial interest associated with eggshell quality. An analysis and comparison of the protein constituents of eggshells of several species would contribute to a better understanding of the shell mineralization process. The recent publication of the turkey genome sequence now provides a basis for the in-depth analysis of the turkey eggshell proteome.ResultsProteomic analysis of turkey acid-soluble and acid-insoluble organic eggshell matrix yielded 697 identified proteins/protein groups. However, intensity-based absolute quantification (iBAQ) results indicated that the 47 most abundant identified proteins already constituted 95% of the total turkey eggshell matrix proteome. Forty-four of these proteins were also identified in chicken eggshell matrix previously. Despite these similarities there were important and unexpected differences. While ovocleidin-116 and ovocalyxin-36 were major proteins constituting approximately 37% of the identified proteome, other members of the group of so-called eggshell-specific proteins were not identified. Thus ovocalyxin-21 and ovocalyxin-32 were missing among matrix proteins. Conversely, major turkey eggshell proteins were not detected in chicken, such as the bone protein periostin, the mammalian counterpart of which is involved in many aspects of bone metabolism and which represented 10-11% of the total identified proteome.ConclusionsEven members of the same avian family show important differences in eggshell matrix composition and more studies on the proteome and the transcriptome level will be necessary to identify a common toolkit of eggshell mineralization and to work out species differences among functional eggshell protein sets and their role in eggshell production.

The Lottia gigantea shell matrix proteome: re-analysis including MaxQuant iBAQ quantitation and phosphoproteome analysis

“…Included in protein identification is quantitation, which was done using exponentially modified protein abundance index (emPAI) [41] previously [17], but was recently superseded [60] in favor of the more accurate automated iBAQ method [19] as implemented in more recent versions of MaxQuant. We believe that this approach is well suited to identify candidates for functional matrix proteins, most likely found among the most abundant components, while retaining all of the information about trace components, irrespective of whether these may have a function in biomineralization or not, and irrespective of whether they are intra-crystalline or belong to the extra-crystalline matrix.…”

Differences in the seminal plasma proteome are associated with oxidative stress levels in men with normal semen parameters

“…The false discovery rate was set to 1% and was determined by searching in a reverse database. Quantification was performed through label-free quantification, using intensity-based absolute quantification (iBAQ), in which protein content is normalized to the total number of potential peptides (26).…”

Dietary calcium deficiency in laying ducks impairs eggshell quality by suppressing the process of shell biomineralization

“…OC-17) have not been confirmed in ducks. As one of the eggshell matrix proteins, OC-116 has been demonstrated to be the most abundant protein in the identified chicken eggshell proteome (Mann et al, 2007;Mann and Mann, 2013) and the single nucleotide polymorphisms (SNPs) in the OC-116 gene are shown to be significantly associated with the eggshell elastic modulus and thickness, and with egg shape (Dunn et al, 2009). Ovocalyxin-32 (OCX-32) is enriched in the cuticle layer of the eggshell and functions to inhibit the spontaneous precipitation of calcium carbonate during the terminal phase of eggshell formation (Gautron et al, 2001).…”