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341lecture04jan30sakai

341lecture04jan30sakai - Cell Biology 341 Last lecture...

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Cell Biology 341 Monday, January 30, 2012 Today: A special type of helix: the amphiphilic α helix Examples of tertiary and quaternary protein structure Finish chapter 2 on thermodynamic limitations on enzyme activity See your DVD for chapter 3 videos, especially α helix, β sheet, disulfide bonds, coiled-coil, SH2 domain, oligomeric proteins, and EF-Tu Also see video 25.2 on antibody structure Last lecture: Amino acids are linked by peptide bonds in proteins The primary structure of a protein is the sequence of amino acids All four types of noncovalent forces participate in determining the 3-dimensional structure of a protein Nonpolar residues are usually found in the interior of a globular protein due to hydrophobic forces 2200 α helix and β sheet are secondary structures formed by hydrogen bonding between peptide bond atoms
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Amphiphilic α helices can form a coiled-coil An amphiphilic α helix has nonpolar amino acid R-groups on one face, and polar amino acid R-groups on the opposite face Figure 3-9 Amphiphilic helices are found in globular proteins with the hydrophobic side facing the interior Two (or three) amphiphilic helices can twist together to form a coiled-coil in which hydrophobic forces push the nonpolar R-groups to the inside of the coil (Driving force to make coiled- coil hydrophobic forces) See the coiled-coil video on your DVD Examples: fibrinogen(triple coiled-coil; involved in blood clotting), α-keratin, leucine zippers(transcription activators), myosin(used in muscles) Red = hydrophobic, non- polar; Green = hydrophilic, polar
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The complete 3-dimensional conformation is called the tertiary structure . Tertiary structure includes the interactions
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341lecture04jan30sakai - Cell Biology 341 Last lecture...

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