W5-S1-Y2 Fibrous proteins.pdf

COURSE NAME: fibrous proteins COURSE CODE: BIO202 Year 2, first semester. WEEK 5 CLO 2 Prof. Naglaa Raafat DEPARTMENT OF BIOMEDICAL SCIENCES 1 DUBAI MEDICAL COLLEGE FOR GIRLS (DMCG), 2023...

COURSE NAME: fibrous proteins COURSE CODE: BIO202 Year 2, first semester. WEEK 5 CLO 2 Prof. Naglaa Raafat DEPARTMENT OF BIOMEDICAL SCIENCES 1 DUBAI MEDICAL COLLEGE FOR GIRLS (DMCG), 2023. ©2023 by DMCG. This work were first developed for the Dubai Medical College for Girls (DMCG) 2023 and is licensed under a Creative Commons Attribution-Non Commercial-Share Alike 4.0 International License.  Fibrous Proteins - They have a structural function in the body, are water-insoluble, and formed of bundles. - Examples: Collagen, Elastin, Keratin. IF Keries em COLLAGENmostabundantprotieninbody - It is the most abundant protein in our body about 25% of the dry protein weight of the human body. - The type and organization are dictated by the structural role; collagen plays in a particular organ. e.g. a- In extracellular matrix or vitreous humor, collagen is dispersed as a gel to strengthen its structure. b- In tendons: collagen is bundled in tight parallel fibers to provide great strength. c- In the cornea: collagen is stacked to transmit light with minimum scattering. d- In cartilage, the organic matrix of bones 2 DUBAI MEDICAL COLLEGE FOR GIRLS (DMCG), 2023. ©2023 by DMCG. This work were first developed for the Dubai Medical College for Girls (DMCG) 2023 and is licensed under a Creative Commons Attribution-Non Commercial-Share Alike 4.0 International License.  1. Structure of Collagen: 1. Primary structure: Amino acids sequence (Gly -X-Y): Very rich in glycine (35%), proline, hydroxyproline, hydroxylysine (21%), and alanine (11%) X----- Proline, Y------Hydroxyproline or Hydroxylysine or others. 2. Secondary structure: formed of right-handed alpha helix 3. Tertiary structure: It consists of three polypeptides, called alpha-chains, which wrap around each other in a triple helix, forming a rope-like structure. Different alpha-chains are depending on the variation of amino acids. 4. Quaternary structure: The collagen has a side chain outside allowing interaction between triple-helical molecules to form long fibrils which condense to form fibers. 5.. 6. Glycosylation:   3 DUBAI MEDICAL COLLEGE FOR GIRLS (DMCG), 2023. ©2023 by DMCG. This work were first developed for the Dubai Medical College for Girls (DMCG) 2023 and is licensed under a Creative Commons Attribution-Non Commercial-Share Alike 4.0 International License.   BIOSYNTHESIS OF COLLAGEN:FFHGase.EC 1.Formation of pre-pro-collagen: in endoplasmic reticulum (ER). 2.Formation of pro-collagen: by break of extra-sequence in ER. sine 3.Hydroxylation: Hydroxy-proline and hydroxy-lysine are formed by post- Fails I translational modification in smooth ER to stabilize the helix. this reaction needs vitamin C as a coenzyme. on 4.Glycosylation: glucose or galactose may be linked to the OH group of a 3 Hothydroxy-lysine in Golgi. 5.Assembly to form triple helix in Golgi. 6.Secretion: By Golgi vesicle to extracellular matrix. 7.Extra-cellular cleavage of pro-collagen: removal of terminal peptide outside the cell. 8.Formation of collagen fibrils: by condensation of several molecules of collagen. 9.Cross-link formation: between hydroxyl-Lys by lysyl oxidase enzyme to strengthen collagen bundles and form large fibers. 4 DUBAI MEDICAL COLLEGE FOR GIRLS (DMCG), 2023. ©2023 by DMCG. This work were first developed for the Dubai Medical College for Girls (DMCG) 2023 and is licensed under a Creative Commons Attribution-Non Commercial-Share Alike 4.0 International License.  5v DUBAI MEDICAL COLLEGE FOR GIRLS (DMCG), 2023. ©2023 by DMCG. This work were first developed for the Dubai Medical College for Girls (DMCG) 2023 and is licensed under a Creative Commons Attribution-Non Commercial-Share Alike 4.0 International License.  Clinical correlation:  What is the effect of Vitamin C deficiency on the biosynthesis of collagen: Vitamin C is needed for the hydroxylation of proline and lysine, so its deficiency inhibits the hydroxylation step Effect: decrease the tensile strength of the assembled fibers which leads to weak tissues manifested by poor wound healing, loose teeth, and bleeding gums. This disease is called scurvy. Scurvy  What is the effect of a mutation that interferes with the ability of collagen to form cross-linked fibrils? It results in a decrease in the tensile strength needed for proper function.  Collagen Diseases: Cause or Defect: mutation in Gly AA in the gene of collagen or genes of some synthetic enzymes. Effect: According to the affected gene several diseases are recorded, e.g.:  Ehlers-Danlos Syndrome: nine different types - lysyl hydroxylaseenzyme gene deficiency is one of many causes - presentation: hyperextensible skin, hyperflexible joints, weak vessel walls (↑ risk for aneurysm) to 11919 BVdue 6 DUBAI MEDICAL COLLEGE FOR GIRLS (DMCG), 2023. ©2023 by DMCG. This work were first developed for the Dubai Medical College for Girls (DMCG) 2023 and is licensed under a Creative Commons Attribution-Non Commercial-Share Alike 4.0 International License.  - Osteogenesis imperfecta (brittle bone syndrome): It’s characterized by easy fracture of bone, retarded wound healing, and hump-back appearance. heating EhlerDanlos syndrome 7 DUBAI MEDICAL COLLEGE FOR GIRLS (DMCG), 2023. ©2023 by DMCG. This work were first developed for the Dubai Medical College for Girls (DMCG) 2023 and is licensed under a Creative Commons Attribution-Non Commercial-Share Alike 4.0 International License.  ELASTIN It Elastin is a connective tissue protein with rubber-like properties. e.g. in the lung, wall of blood vessels, and ligaments. proline AÉy Ana m Val  Structure: -Consists of small, non-polar amino acids e.g. glycine, alanine, and valine. Moreover, elastin is rich in proline, lysine, and hydroxyproline. -Interchain cross-links: elastin fibers cross-link through 4 lysine amino acids (desmosine cross-link). EE i 8 DUBAI MEDICAL COLLEGE FOR GIRLS (DMCG), 2023. ©2023 by DMCG. This work were first developed for the Dubai Medical College for Girls (DMCG) 2023 and is licensed under a Creative Commons Attribution-Non Commercial-Share Alike 4.0 International License.   Clinical correlation: Role of alpha1-antitrypsin (α1 -AT) in elastin degradation: Protein α1 -AT inhibits elastase and trypsin. These enzymes are secreted by the liver, monocytes, and alveolar macrophages and digest elastin.  Deficiency of alpha-1 AT permits neutrophil elastase to destroy the lung. The time result in loss of elasticity and fibrosis of the lung which always inflated like a full balloon (lung emphysema) 1 at AT 9S n I AT neutrophil iing elasticity ung emphysema 9 DUBAI MEDICAL COLLEGE FOR GIRLS (DMCG), 2023. ©2023 by DMCG. This work were first developed for the Dubai Medical College for Girls (DMCG) 2023 and is licensed under a Creative Commons Attribution-Non Commercial-Share Alike 4.0 International License.   What is the difference between elastin and collagen Elastin Collagen 1. 3ry structure Random coil Triple helix Bag 2. Pro-sequence. Pro Absent Pro Present 3. CHO. Absent Present CHO CHO 4. Genetic types One V1 Several VE 5. OH lysine. Absent OHlysine Present OHlysine 6. Desmosine Present Desmo Absent cross-links Desmo 7. Rubber-like structure Present IS Absent 0 0 10 DUBAI MEDICAL COLLEGE FOR GIRLS (DMCG), 2023. ©2023 by DMCG. This work were first developed for the Dubai Medical College for Girls (DMCG) 2023 and is licensed under a Creative Commons Attribution-Non Commercial-Share Alike 4.0 International License.  Keratins  Types of Keratins  Keratin: Formed of helixes and present in the epidermal layer of skin, nails, and hair. Rich in cysteine has Karen  Keratin: very rich in glycine and alanine, arranged in sheets. Present in silk protein, reptiles, and feathers of birds. B si 11 DUBAI MEDICAL COLLEGE FOR GIRLS (DMCG), 2023. ©2023 by DMCG. This work were first developed for the Dubai Medical College for Girls (DMCG) 2023 and is licensed under a Creative Commons Attribution-Non Commercial-Share Alike 4.0 International License.  Permanent Hair Wave (reading) Hair keratin consists of many protein alpha-helices. Three alpha-helices are interwoven into a left-handed coil called a protofibril. Eleven protofibrils are bonded and coiled together to make a microfibril. Hundreds of these microfibrils are cemented into an irregular bundle called a microfibril. These in turn are mixed with dead and living cells to make a complete strand of hair. The alpha-helices are extensively cross-linked with disulfide bonds from cysteine. These bonds enable keratin to have a somewhat elastic nature. If the alpha- helices stretch unevenly past each other, the disulfide cross-links return them to the original position when the tension is released. Disulfide Bonds: Different protein chains or loops within a single chain are held together by strong covalent disulfide bonds. The alpha-helices in the hair strands are bonded by disulfide links. Use Reducing Agent: In the permanent wave process, a basic reducing substance (usually bisulfite or thioglycolate) is first added to reduce and rupture some of the disulfide cross-links. Temporary Wave: When the hair gets wet, water molecules intrude into the keratin strands. The sheer numbers of water molecules can disrupt some of the hydrogen bonds which also help to keep the alpha-helices aligned. The helices can slip past each other and will retain a new shape in the hair-drying process as new hydrogen bonds are formed. The hair strands are able for a short time to maintain the new curl in the hair. 12 DUBAI MEDICAL COLLEGE FOR GIRLS (DMCG), 2023. ©2023 by DMCG. This work were first developed for the Dubai Medical College for Girls (DMCG) 2023 and is licensed under a Creative Commons Attribution-Non Commercial-Share Alike 4.0 International License.  Permanent Wave: For a permanent wave, we will continue the discussion from the use of the reducing agent. The hair is put on rollers or curlers. Since the alpha-helices are no longer tightly cross-linked to each other, the alpha-helices can shift positions about each other. An oxidizing agent, usually, a dilute solution of hydrogen peroxide, (also called the neutralizer) is added to reform the disulfide bonds in their new positions. The permanent will hold these new disulfide bond positions until the hair grows out, since new hair growth is of course not treated. 51 52 Enzymes Hemoglobin EneryProd 13 DUBAI MEDICAL COLLEGE FOR GIRLS (DMCG), 2023. ©2023 by DMCG. This work were first developed for the Dubai Medical College for Girls (DMCG) 2023 and is licensed under a Creative Commons Attribution-Non Commercial-Share Alike 4.0 International License.