Lecture8 - Lecture 8 10/10/11 Background reading: Berg, et...

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Lecture 8 10/10/11 Background reading: Berg, et al.: pages 43 -48 Garrett and Grisham: Chapter 6: Pages 194-201 Outline: ± Fibrous proteins ± Collagen ± Coiled-coil proteins ± Globular proteins ± Myoglobin ± Heme group ± Quaternary structure (IV structure) of proteins ± Hemoglobin ± Comparison of hemoglobin with myoglobin
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In general, proteins can be grouped into three large categories based on their structures and solubility: 1) Fibrous proteins 2) Globular proteins 3) Membrane proteins Fibrous proteins Fibrous proteins tend to have simple, regular linear structures and are often found to play structural roles in the cell and extracellular matrix. Collagen Class of proteins that are the most abundant proteins in mammals. Extracellular proteins found in skin, bone, cartilage, tendons and teeth. Rod-shaped molecule that contains three helical polypeptide chains, each of which contains about 1000 amino acid residues In this diagram each of the chains is shown in a different color.
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The sequence of amino acids in a fragment of collagen is shown below. This sequence demonstrates some unique features of collagen: 1) About one third of the amino acids are glycine residues. 2) The sequence glycine- proline-hydroxyproline recurs frequently. Hydroxyproline is a derivative of proline that has been modified by placing a hydroxyl group in place of one of the H atoms on the pyrrolidine ring. This chemical modification is catalyzed by an enzyme and occurs in the endoplasmicreticulum of the cell after the protein has been synthesized.
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The helical peptide chains of collagen are different from the α -helix structure we have previously seen in that it does not have hydrogen bonds within the strand. The pyrrolidine rings of the proline and hydroxyproline repel one another when the helix is forming and stabilize the helix, which has about 3 residues per turn. Three strands of the helix wind tightly around one another to form a superhelical cable that is stabilized by hydrogen bonds between the imino (NH) groups of glycine and the carbonyl (CO) groups of residues on the other chains.
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This note was uploaded on 01/15/2012 for the course BIS 102 taught by Professor Hilt during the Fall '08 term at UC Davis.

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Lecture8 - Lecture 8 10/10/11 Background reading: Berg, et...

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