Alpha-keratin
Alpha-keratin, or
Structure[edit]
Biochemistry[edit]
Synthesis[edit]
Properties[edit]
The property of most biological importance of alpha-keratin is its structural stability. When exposed to mechanical stress,
Characterization[edit]
Type I and type II[edit]
Alpha-keratins proteins can be one of two types: type I or type II. There are 54 keratin genes in humans, 28 of which code for type I, and 26 for type II.[12] Type I proteins are acidic, meaning they contain more acidic amino acids, such as aspartic acid, while type II proteins are basic, meaning they contain more basic amino acids, such as lysine.[13] This differentiation is especially important in alpha-keratins because in the synthesis of its sub-unit dimer, the coiled coil, one protein coil must be type I, while the other must be type II.[2] Even within type I and II, there are acidic and basic keratins that are particularly complementary within each organism. For example, in human skin, K5, a type II alpha keratin, pairs primarily with K14, a type I alpha-keratin, to form the alpha-keratin complex of the epidermis layer of cells in the skin.[14]
Hard and soft[edit]
Hard alpha-keratins, such as those found in nails, have a higher cysteine content in their primary structure. This causes an increase in disulfide bonds that are able to stabilize the keratin structure, allowing it to resist a higher level of force before fracture. On the other hand, soft alpha-keratins, such as ones found in the skin, contain a comparatively smaller amount of disulfide bonds, making their structure more flexible.[1]
References[edit]
- ^ a b G., Voet, Judith; W., Pratt, Charlotte (2016-02-29). Fundamentals of biochemistry : life at the molecular level. ISBN 9781118918401. OCLC 910538334.
{{cite book}}
: CS1 maint: multiple names: authors list (link) - ^ a b c d e Wang, Bin; Yang, Wen; McKittrick, Joanna; Meyers, Marc André (2016-03-01). "Keratin: Structure, mechanical properties, occurrence in biological organisms, and efforts at bioinspiration" (PDF). Progress in Materials Science. 76: 229–318. doi:10.1016/j.pmatsci.2015.06.001.
- ^ Burkhard, Peter; Stetefeld, Jörg; Strelkov, Sergei V (2001). "Coiled coils: a highly versatile protein folding motif". Trends in Cell Biology. 11 (2): 82–88. doi:10.1016/s0962-8924(00)01898-5. PMID 11166216.
- ^ Pace, C N; Scholtz, J M (1998-07-01). "A helix propensity scale based on experimental studies of peptides and proteins". Biophysical Journal. 75 (1): 422–427. Bibcode:1998BpJ....75..422N. doi:10.1016/S0006-3495(98)77529-0. ISSN 0006-3495. PMC 1299714. PMID 9649402.
- ^ Steinert, Peter M.; Steven, Alasdair C.; Roop, Dennis R. (1985). "The molecular biology of intermediate filaments". Cell. 42 (2): 411–419. doi:10.1016/0092-8674(85)90098-4. PMID 2411418. S2CID 8922569.
- ^ McKittrick, J.; Chen, P.-Y.; Bodde, S. G.; Yang, W.; Novitskaya, E. E.; Meyers, M. A. (2012-04-03). "The Structure, Functions, and Mechanical Properties of Keratin". JOM. 64 (4): 449–468. Bibcode:2012JOM....64d.449M. doi:10.1007/s11837-012-0302-8. ISSN 1047-4838. S2CID 45028832.
- ^ Windoffer, Reinhard; Beil, Michael; Magin, Thomas M.; Leube, Rudolf E. (2011-09-05). "Cytoskeleton in motion: the dynamics of keratin intermediate filaments in epithelia". The Journal of Cell Biology. 194 (5): 669–678. doi:10.1083/jcb.201008095. ISSN 0021-9525. PMC 3171125. PMID 21893596.
- ^ Kölsch, Anne; Windoffer, Reinhard; Würflinger, Thomas; Aach, Til; Leube, Rudolf E. (2010-07-01). "The keratin-filament cycle of assembly and disassembly". J Cell Sci. 123 (13): 2266–2272. doi:10.1242/jcs.068080. ISSN 0021-9533. PMID 20554896.
- ^ Eckhart, Leopold; Lippens, Saskia; Tschachler, Erwin; Declercq, Wim (2013-12-01). "Cell death by cornification". Biochimica et Biophysica Acta (BBA) - Molecular Cell Research. 1833 (12): 3471–3480. doi:10.1016/j.bbamcr.2013.06.010. PMID 23792051.
- ^ Pan, Xiaoou; Hobbs, Ryan P; Coulombe, Pierre A (2013). "The expanding significance of keratin intermediate filaments in normal and diseased epithelia". Current Opinion in Cell Biology. 25 (1): 47–56. doi:10.1016/j.ceb.2012.10.018. PMC 3578078. PMID 23270662.
- ^ Kreplak, L.; Doucet, J.; Dumas, P.; Briki, F. (2004-07-01). "New Aspects of the
α -Helix toβ -Sheet Transition in Stretched Hardα -Keratin Fibers". Biophysical Journal. 87 (1): 640–647. Bibcode:2004BpJ....87..640K. doi:10.1529/biophysj.103.036749. PMC 1304386. PMID 15240497. - ^ Moll, Roland; Divo, Markus; Langbein, Lutz (2017-03-07). "The human keratins: biology and pathology". Histochemistry and Cell Biology. 129 (6): 705–733. doi:10.1007/s00418-008-0435-6. ISSN 0948-6143. PMC 2386534. PMID 18461349.
- ^ Strnad, Pavel; Usachov, Valentyn; Debes, Cedric; Gräter, Frauke; Parry, David A. D.; Omary, M. Bishr (2011-12-15). "Unique amino acid signatures that are evolutionarily conserved distinguish simple-type, epidermal and hair keratins". Journal of Cell Science. 124 (24): 4221–4232. doi:10.1242/jcs.089516. ISSN 0021-9533. PMC 3258107. PMID 22215855.
- ^ Lee, Chang-Hun; Coulombe, Pierre A. (2009-08-10). "Self-organization of keratin intermediate filaments into cross-linked networks". The Journal of Cell Biology. 186 (3): 409–421. doi:10.1083/jcb.200810196. ISSN 0021-9525. PMC 2728393. PMID 19651890.