BIOC 212 Lecture Notes - Lecture 33: Protein Precursor, Monosaccharide, Disaccharide
29 May 2018
School
Department
Course
Professor
Cell Junctions & Cell Adhesion XIII
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Integrin-Mediated Fibronectin Assembly
• Fibronectin assembles into multimeric form
• Cell initially secretes fibronectin as homodimer
o Held together by disulfide bonds
o Both dimers are curled up --protein can diffuse onto cell surface, is soluble
• Then bind respective integrin through RDG
o Tethers to cell surface
o i.e. a5b1 integrin interacts with fibronectin
• Integrin connected through actin filaments
• Actin filaments, in combination with myosin, puts force and move integrins apart
(contractile)
o Through the generation of this tension, the curled up molecules are opened
up --> now have opened conformation of two fibronectin subunits
o Opens up assembly sites that help them bind other fibronectin molecules
• Mainly on N-terminus of fibronectin
• Can then quickly get extracellular fiber formation, providing basis for
collagen to form
Collagen
• Fibrous proteins found in all multi-cellular animals
o 25% of total protein mass
• Composed of three polypeptide chains
o Each monomer of collagen has three subunits
o Alpha chains
o 3 alpha chains form collagen triple helix
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• 42 collagen genes in humans – 27 collagen types
o Not every product of collagen gene can interact with another one (specific)
o Clear selection
• Fibril-forming & sheet forming collagens
o Some form long extended fibers, other form networks
o Wide variety of collagen structures in ECM
• Exist as homotrimers or heterotrimers
o Triple helices can consist of same gene product or heterotrimer made of
different gene products
• Form aggregates by association of triple helices
