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Not to be confused with beta-carotene.

β-keratin or beta-keratin is a protein in the keratin family. β-keratin is rich in stacked β pleated sheets, in contrast to alpha-keratin, a fibrous protein rich in alpha helices[citation needed].

β-keratin is found in reptiles.[1][2] It adds much more rigidity to reptilian skin than alpha-keratin does to mammalian skin.

β-keratin is impregnated into the stratum corneum of the reptilian skin, providing waterproofing and the prevention of desiccation.

In birds, scales, beaks, claws and feathers also contain β-keratin of the avian family. Phylogenetic studies of β-keratin sequences show that feather β-keratins evolved from scale β-keratins.[3] The scale β-keratins form the basal group in avians. Duplication and divergence events then led to claw β-keratin genes, and further recombination resulted in new feather and feather-like avian β-keratin genes. Evidence for these duplication events comes from the correlation of feather β-keratin clade structure with their genomic loci.[4]

Changes in β-keratins may have also influenced the development of powered flight. A recent study using molecular dating methods to link the evolution of avian β-keratin genes in general to that of feathers specifically reveals that the avian β-keratin family began diverging from the crocodile family about 216 million years ago.[4] But the feather β-keratin family did not begin diverging until 125 million years ago, a date consistent with the adaptive radiation of birds during the Cretaceous. β-keratins found in modern feathers have increased elasticity, a factor that may have contributed to their role in flight.[4] Thus, the feathered ancestors of birds including Anchiornis and Archaeopteryx, whose flight capabilities have been questioned,[5] would have had avian, but not feather β-keratins.

The small alvarezsaurid dinosaur Shuvuuia deserti showed evidence of a featherlike skin covering. Analysis by Schweitzer et al. (1999) showed that these featherlike structures consisted of beta-keratin.[6]

References[edit]

  1. ^ Dalla Valle L, Nardi A, Belvedere P, Toni M, Alibardi L (July 2007). "Beta-keratins of differentiating epidermis of snake comprise glycine-proline-serine-rich proteins with an avian-like gene organization". Dev. Dyn. 236 (7): 1939–53. doi:10.1002/dvdy.21202. PMID 17576619. 
  2. ^ Dalla Valle L, Nardi A, Toffolo V, Niero C, Toni M, Alibardi L (February 2007). "Cloning and characterization of scale beta-keratins in the differentiating epidermis of geckoes show they are glycine-proline-serine-rich proteins with a central motif homologous to avian beta-keratins". Dev. Dyn. 236 (2): 374–88. doi:10.1002/dvdy.21022. PMID 17191254. 
  3. ^ Greenwold, M.J.; Sawyer, R.H. (2010). "Genomic organization and molecular phylogenies of the beta (β) keratin multigene family in the chicken (Gallus gallus) and zebra finch (Taeniopygia guttata): implications for feather evolution". BMC Evolutionary Biology 10. doi:10.1186/1471-2148-10-148. 
  4. ^ a b c Greenwold, M.J.; Sawyer, R.H. (2011). "Linking the molecular evolution of avian beta (β) keratins to the evolution of feathers". Journal of Experimental Zoology 316B: 609–616. doi:10.1002/jez.b.21436. 
  5. ^ Nudds, R.L.; Dyke, G.J. (14 May 2010). "Narrow Primary Feather Rachises in Confuciusornis and Archaeopteryx Suggest Poor Flight Ability". Science 328: 887–889. doi:10.1126/science.1188895. PMID 20466930. 
  6. ^ .Schweitzer, Mary Higby, Watt, J.A., Avci, R., Knapp, L., Chiappe, L, Norell, Mark A., Marshall, M. (1999). "Beta-Keratin Specific Immunological reactivity in Feather-Like Structures of the Cretaceous Alvarezsaurid, Shuvuuia deserti Journal of Experimental Biology (Mol Dev Evol) 255:146-157

External links[edit]

There are two main forms of keratin, alpha-keratin and beta-keratin. Alpha-keratin is seen in humans and other mammals, beta-keratin is present in birds and reptiles. Beta-keratin is harder than alpha-keratin. Structurally alpha-keratin have alpha-helical coiled coil structure while beta-keratin have twisted beta sheet structure.bIn the case of β-sheets, this allows sterically-unhindered hydrogen bonding between the amino and carboxyl groups of peptide bonds on adjacent protein chains, facilitating their close alignment and strong binding. Fibrous keratin molecules can twist around each other to form helical intermediate filaments.

SILK:- The secondary structure of silk is an example of the beta pleated sheet. In this structure, individual protein chains are aligned side-by-side with every other protein chain aligned in an opposite direction.The chains are antiparallel, with an alternating C → N orientation. The protein chains are held together by intermolecular hydrogen bonding, that is hydrogen bonding between amide groups of two separate chains. This intermolecular hydrogen bonding in the beta-pleated sheet is in contrast to the intramolecular hydrogen bonding in the alpha-helix.

The hydrogen on the amide of one protein chain is hydrogen bonded to the amide oxygen of the neighboring protein chain. The pleated sheet effect arises form the fact that the amide structure is planar while the "bends" occur at the carbon containing the side chain.

Fortunately, the "side" chain R groups in silk are not very bulky. The basic primary structure of silk consists of a six amino acid unit that repeats itself. The sequence where every other unit is glycine in silk is: -gly-ala-gly-ala-gly-ala-. Although glycine and alanine make up 75-80% of the amino acids in silk, another 10-15% is serine and the final 10% contain bulky side chains such as in tyr, arg, val, asp, and glu.


Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Beta-keratin — Please support Wikipedia.
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106 news items

WOAI

WOAI
Wed, 13 Apr 2016 17:14:15 -0700

"They might flavor it with beta keratin and maybe color it with a little chlorophyll to make it a little more green so you have a lower quality cheaper oil," Messina told us. In order to have an "ultra premium" label, the oil must contain 100% of ...

WFLA

WFLA
Fri, 08 Apr 2016 02:22:30 -0700

“They might flavor it with beta keratin, and maybe color it with a little chlorophyll to make it a little more green so you have a lower quality cheaper oil.” said Messina. From farming and milling, to transportation, the new Ultra Premium labeling UP ...

Sci-News.com

Sci-News.com
Thu, 30 Jul 2015 07:03:34 -0700

They discovered that within the cuticle a key diffraction feature of the alpha keratin is absent – indicating the presence of beta keratin instead of the alpha keratin phase. Until now, it was believed that keratin in the whole hair had only an alpha ...

The Scientist

The Scientist
Fri, 08 Jan 2016 06:14:52 -0800

Left: Myxozoan spores (K. iwatai), each about 10 micrometres in diameter. Right: a moon jellyfish (Aurelia aurita), about 25 centimeters across.LEFT: UNIVERSITY OF KANSAS, A. DIAMANT; RIGHT: UNIVERSITY OF KANSAS, P. CARTWRIGHT (VIA ...

The Japan Times

The Japan Times
Tue, 24 Nov 2015 21:17:14 -0800

The scientists found in Gekko japonicus an expansion in the genes related to beta-keratin, accounting for the gecko's ability to generate its setae. No such expansion exists in the genomes of other reptiles lacking the ability to walk on smooth ...

1011now

1011now
Thu, 03 Mar 2016 11:18:45 -0800

"I designed it basically to assist peoples' immune systems, especially the carrots and oranges which provide a huge level of vitamin C and beta keratin and then the turmeric acts as a natural anti-inflammatory," said Day. And as all restaurants have ...

Phys.Org

Phys.Org
Thu, 28 Jan 2016 03:00:25 -0800

Additionally, the scientists discovered that the cuticle has a diffraction signal—a type of x-ray derived "fingerprint"—that is characteristic of beta-keratin sheets, and quite different from the spaghetti-like alpha-keratin form found in the cortex ...
 
Phys.Org
Tue, 24 Nov 2015 14:00:13 -0800

Moreover, beta-keratin genes within and outside of the EDC have acquired specific expression in the scutes of the turtle shell. Molecular phylogenetic analyses lead the authors to hypothesize that these specialized shell beta-keratins have evolved from ...
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