Proteins of Extracellular Matrix PDF

Proteins of Extracellular Matrix dr/ mostafa mohamed mostafa assistant professor of clinical biochemistry and molecular biology  Classification of proteins according to their conformation: as.is b...

Proteins of Extracellular Matrix dr/ mostafa mohamed mostafa assistant professor of clinical biochemistry and molecular biology  Classification of proteins according to their conformation: as.is b eh Fibrous Proteins Globular Proteins Arrangement of parallel form along folded into polypeptide chain a single axis to compact spherical yield long fibers or globular shapes. Solubility in Insoluble Soluble water Function supportive or mobile function protective Carriar Examples Collagen and Enzymes and elastin mostcommen Hemoglobin.  Ema -Extracellular matrix is the connective tissue surrounding the cells & organs. -Extracellular Matrix contains 2 types of proteins: salem d A- Structural proteins e.g. collagen & elastin. www B- Specialized proteins as fibronectin & fibrillin.  Collagen as a a 213 - It is a fibrous protein - Formed by C.T cells (fibroblasts). - Present in skin, bones, cartilages, tendons, lungs, liver, vessels and cornea. in legament - Forms 25% of total body proteins.  Structure -Tropocollagen is the building unit. - It is a long , thin protein. - It consists of three α Chains. 3polypiptites chain - Each chain is a left handed helix. The three left handed chains are tightly twisted to form a right handed superhelix (tropocollagen molecule). sina.SI Tropocollagen triple helix  Amino acid composition: - The (α-chains), contain the repeating sequence Gly-X-Y, where: nomads Gly is glycine. iii iii hydroxyprolinprolin X position: usually occupied by Proline, pro Garonne proinnation rain simple that protin protin sometimes lysine. continsust acid Amino Y position: usually occupied by hydroxyproline sometimes hydroxylysine. soso.su region - Glu or Gal are attached to hydroxylysine, So collagen is considered as glycoprotein. swear hydroxylisin a  Types of Collagen: - More than twenty types of collagen. mins Ew - Variations in the amino acid sequence of the α-chain result in different α-chains which are combined to form various types of collagen found in the tissues. - The most common types of collagen are type I and type II. ÑI it is - Type I: (α12α2) Main type present in Bones - Type II: (α13) Main type present in cartilage  Synthesis of collagen A) Intracellular processing 1- Synthesis of preprocollagen α chain: by ribosomes on rough endoplasmic reticulum. - preprocollagen α chain is formed of : N terminal signal peptide, 2 extension peptides ( at C and N terminal) and procollagen α chain. TBody - Signal peptide directs the polypeptide chain into the ER. Body 2- Conversion of the pre procollagen α chain to procollagen α chain: a - Removal of the signal peptide by signal peptidase. on on si id g - Hydroxylation: of proline and lysine by prolyl & lysyl hydroxylase to form hydroxyproline & I rain hydroxylysine. oHavony nedroxepr.in Co-factor for both hydroxylases: vitamin C. - Glycosylation: of some hydroxylysines by glucosyl or galactosyl transferase. 3- Formation of procollagen: inextinstion SH - Oxidation of cysteine residues and formation of 6 disulfide bonds at C-terminal extension peptides to initiate and form triple helix. cn final bond disulfide cut Prepro i 3 pro I proclay α chain c c 61 1 Ibone salted 00 B) Extracellular processing: 1- Formation of tropocollagen: Removal of the two extension peptides from the amino and carboxyl terminals. Catalyzed by two enzymes: procollagen aminoproteinase & procollagen carboxyproteinase. 2- The triple helix is further stabilized: by formation of inter-chain cross linkages. I 3- Collagen fibril and fiber formation: The newly formed tropocollagen molecules assemble in a parallel and staggered array into collagen fibrils. um These fibrils are then packed together to form collagen fibers. 1 4- Maturation of the collagen: Collagen fibers are further stabilized by the formation of covalent cross-links.  www o Osteogenesis Imperfecta Syndrome Brittle bone syndrome. ameblo.it Replacement of glycine residues by larger amino acids. Manifestations: easily bones fracture, loose joints and poor muscle tone. eby.IT  Elastin Rubber like protein. found in ligaments, lungs, walls of blood vessels. Elastin is rich in proline, little hydroxyproline, No hydroxylysine. Building unit: tropoelastin. Elastin is fibrous when extended, globular when relaxed. It is highly elastic and can be stretched in different directions due to its desmosine cross link with the special arrangement of its chains into α chains and random sequences.  spishilsedpr.tn 3- Fibronectin inblad - is a glycoprotein of ECM and in plasma. a nearer - Function: adhesion of cells to ECM. - Structure: 2 identical polypeptide chains joined by disulfide s-s bridges. - It has several binding sites for: heparin, cell surface receptors (integrins). Integrins are transmembrane adhesion receptors. xp polypiptidchian bon  4- Fibrillin: renaming cold commindisses It is a large glycoprotein secreted by fibroblasts. It is found in the suspensory ligament of the eye lens, and with elastin in the aorta and periosteum. Marfan's syndrome: gene defect in fibrillin gene. dislocation as wsz.io Eyes: ectopia lentis or dislocation of lens. CVS: weakness of aorta & dilatation of ascending t.it gn aorta. 1 Skeletal system: patients are tall & have long digits. Joints: hyperextensibility. w w.t.ws Thank you