Corneous beta proteins
The formerly known beta-keratins are now known as Corneous beta proteins, CBPs. This is to avoid confusion with intermediate filament keratin alpha and beta, which are true keratins.[1]
The structure that characterizes the squamates scales mechanical strength are the beta-sheets, as in feathers and other sauropsids these structures are produced from the corneous beta proteins which is expressed at a different strata in the epidermis compared to keratin. They are expressed in the epidermal differentiation complex, EDC. The process between keratin and CBPs is different, the assembly of keratin occurs in rods dimerization and then head to tail interaction, where for CBPs, first the beta-sheets form a dimer, which interact with other dimers making a very thin filament. The beta-sheets produced by CBPs are produced mainly by the aminoacid residue valine, while for keratin, they are derived from alanine residues, longer than 10 residues will form an alpha helix. The gene location, the protein formation or structure processes between keratins and CBPs differ. Because they are two different genes and processes they should also be called differently. When referred to sauropsid beta-sheet structure it should be addressed as CBPs. The beta-sheets form in four antiparallel sheets, forming a nanocrystal which provides rigidity and strength. The aminoacid sequence has 34 conserved aminoacid residues. The beta-sheets will form a dimer structure, then will bind to another dimer forming a filament that can be 3–3.4nm in diameter.[2][3][4][1]
References
- ↑ 1.0 1.1 Calvaresi, M., Eckhart, L., Alibardi, L.(2016). "The Process of Cornification Evolved From the Initial Keratinization in the Epidermis and Epidermal Derivatives of Vertebrates: A New Synthesis and the Case of SauropsidsInternational Review of Cell and Molecular Biology. DOI: 10.1016/bs.ircmb.2016.06.005 Cite error: Invalid
<ref>tag; name "alibardi, 2016." defined multiple times with different content - ↑ Alibardi, L.(2016). "Sauropsids Cornification is Based on Corneous Beta-Proteins, a Special Type of Keratin-Associated Corneous Proteins of the EpidermisJEZ-B Moleculear and developmental evolution. DOi:10.1002/jez.b.22689
- ↑ Holthaus, K. B., Eckhart, L., Dalla Valle, L., Alibardi, L.(2018). "Review: Evolution and diversification of corneous beta-proteins, the characteristic epidermal proteins of reptiles and birdsJEZ-B Moleculear and developmental evolution. DOI: 10.1002/jez.b.22840
- ↑ Calvaresi, M., Eckhart, L., Alibaridi, L.(2016). "The molecular organization of the beta-sheet region in Corneous beta-proteins (beta-keratins) of sauropsids explains its stability and polymerization into filamentsJournal of Structural Biology. DOI: 10.1016/j.jsb.2016.03.004
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