Sept 1 - Biochem 423 Robert A Orlando Ph.D PROTEIN...

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Unformatted text preview: Biochem 423 Robert A. Orlando, Ph.D. PROTEIN STRUCTURE AND FOLDING PEPTIDE BOND FORMATION – CONDENSATION REACTION PROTEINS COME IN VARIOUS SIZES – (SOME EXAMPLES) 30 | P a g e Biochem 423 Robert A. Orlando, Ph.D. PROTEIN STRUCTURE PRIMARY TO SECONDARY STRUCTURE – REQUIREMENTS Rotation around peptide bond is restricted. 31 | P a g e Biochem 423 Robert A. Orlando, Ph.D. ‐HELIX – MOST COMMON SECONDARY STRUCTURE Polypeptide chain turns to form a “right‐hand” helix. Process is driven by: H‐bonding of peptide backbone Van der Waals repulsions from side chains facing outward ‐SHEET ‐‐ (ALZHEIMER PEPTIDE TRANSITION AS EXAMPLE) Polypeptide chains can be in parallel or anti‐parallel orientation. Side chains come out of top and bottom of ‐sheets. 32 | P a g e Biochem 423 Robert A. Orlando, Ph.D. ‐TURN Polypeptide chain assumes ‐ sheet structure and folds back on itself. 4 amino acids minimum Proline is a “helix‐breaker” can introduce ‐turns SECONDARY TO TERTIARY STRUCTURE – REQUIREMENTS GLOBULAR MOSTLY ‐HELIX ACTIN VERSUS FIBROUS MOSTLY ‐SHEET SILK PROTEIN → COLLAGEN = SPECIAL TRIPLE HELIX FOR STRENGTH SECONDARY STRUCTURES HELD BY SIDE‐CHAIN (INSIDE = HYDROPHOBIC) DISULFIDE BRIDGES (CYSTEINE) EXCLUSION OF WATER FROM HYDROPHOBIC CORE (GLOBULAR) 33 | P a g e Biochem 423 Robert A. Orlando, Ph.D. PROTEIN FOLDING – SEEKING A STABLE ENERGY STRUCTURE SEQUENTIAL PROCESS BEGINNING WITH FORMATION OF SECONDARY STRUCTURES SECONDARY STRUCTURES UNDERGO “RANDOM SAMPLING” FOLDING IS CO‐TRANSLATIONAL TO HELP PROVIDE “ORDER” “MOLECULAR CHAPERONES” ARE SOMETIMES NEEDED TERTIARY TO QUATERNARY STRUCTURE – HEMOGLOBIN 34 | P a g e ...
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This note was uploaded on 12/11/2010 for the course BIOC 423 taught by Professor Robert during the Fall '10 term at New Mexico.

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