Collagen and keratin protein

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This lecture explains about the collagen and keratin protein structure and function of proteins like collagen and keratin. Molecules required for structural functions are in most cases long and skinny, insoluble and organized to form fibres with the aid of associating facet by using part. So much of the epidermis comprises two populations of cells which might be separated by using a thin layer fabricated from a network of fibres - basement membrane. • Above the membrane (surface) cells (epidermal) are embedded in protein fibres of keratin. That is the epidermis. Below the basement membrane is the dermis the deeper layer of the dermis where the cells are embedded in another gruop of protein fibres collagen. • Both of those proteins are very insoluble, both have very excessive tensile force, but their structures are very special on the grounds that capabilities fluctuate. Keratin discovered in dermis, nails, hair, horn and hoof. Collagen observed in dermis, cartilage, bone, tendons. • Strength is offered with the aid of establishing lengthy rods which twist collectively to kind ropes, and are laid down in criss-pass matrix type. Correspondingly, AA sequences in fibrous proteins designed to be long and repetitive and not using a beta-turns or folding characteristics of globular proteins. Fibrous proteins should not have prosthetic companies or active web sites, which want defense. • Very abundant fibrous protein constitutes ¼ of all protein in physique. Observed in dermis, bone, tendon, cartilage, blood vessels and almost all organs the place it serves to kind a matrix (insoluble) for retaining and supporting cells. As in keratin the fundamental constitution is modified to meet the specialised wishes of precise tissues. • The basic unit of structure is a triple helix structure referred to as tropocollagen and every polypeptide chain usually has 1000 AA residues. Analysis of the polypeptide chains exhibits that gly and professional or hydroxypro are very distinguished, virtually one 0.33 of the AA are gly and ¼ is professional or hydroxypro. The polypeptide chain is virtually a repeating unit of a tripeptide unit gly-X-professional where X is another AA and professional will also be Hpro. • Because of the excessive degree of professional or Hpro the polypeptide chains can't undertake both alpha-helix or beta-sheet conformations. Instead, polypeptides expect a left surpassed helix conformation which is stretched and more open than the coiled alpha-helix. • This extra open increased constitution allows the three helices to interlock higher to form a rigid three-stranded cable or triple helix. As a consequence the important constitution plays a central function in producing this fundamental cable structure which offers collagen its major homes. The professional residues preclude alpha-helix formation and aid generate the improved LH triple helix conformation. The gly every three residues is central considering of its very small R workforce takes up little or no house permits the three helices fit very shut collectively. • The unique AA sequence prevents H-bonding inside the chains so one of the crucial pro are hydroxylated to Hpro, which then kind vast inter-chain H-bonding to lock the chains within the conformation. This stabilises the distinguished constitution. With out the H-bonds the constitution is unstable and un-winds. • Hydroxylations on professional are carried out with the aid of an enzyme known as prolyl hydroxylase, which is an enzyme that requires vitamin C as a cofactor within the response. Absence of vitamin C within the food regimen reduces hydroxylation of pro, and collagen fibres begin to break down and new collagen now not formed accurately. Lack of diet C factors scurvy since collagen fibres will not be fashioned safely, and this causes dermis lesions, weakened gums so enamel fall out etc. • Equally fundamental is hydroxy-lys catalysed by means of lysine hydroxylase. Attached to the lys residues are three sugars gal-gal-glu, and these enable H-bonding to occur between triple helices, which is principal for balance of the bigger complex that binds fibres collectively to type a matrix mattress to binds cells to the matrix and form a tissue. • There is a genetic defect referred to as Ehlers-Danlos Syndrome, which produces a faulty lysine hydroxylase leading to bad go-linking between fibres, so collagen is weakly held collectively and unfastened. Makes the dermis very hyperextensible, very skinny translucent in areas, fingers are spidery, joints are hyperflexible. Brought on via a scarcity of hydroxy-lys in collagen so no sugars, and no cross-linking between fibres and with cells. • For more information, log on to- • http://www.shomusbiology.com/ • Get Shomu's Biology DVD set here- • http://www.shomusbiology.com/dvd-store/ • Download the study materials here- • http://shomusbiology.com/bio-material...

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