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CHMI 2227E Biochemistry I

CHMI 2227E Biochemistry I. Proteins: Tertiary structure. Tertiary structure. Secondary structure: Involves a single type of structure: a -helix b -pleated sheet Presence of interactions between amino acids that are close together in the primary structure

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CHMI 2227E Biochemistry I

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  1. CHMI 2227EBiochemistry I Proteins: Tertiary structure CHMI 2227 - E.R. Gauthier, Ph.D.

  2. Tertiary structure CHMI 2227 - E.R. Gauthier, Ph.D.

  3. Secondary structure: Involves a single type of structure: a-helix b-pleated sheet Presence of interactions between amino acids that are close together in the primary structure Main type of interaction: H bonds. Necessary but not sufficient to make a functional protein. Tertiary structure: Involves the folding, in space, of the whole polypeptide chain; Involves several elements of seconday structures, whichy interact together through different interaction forces/bonds: H bonds Electrostatic interactions Van der Waals interactions Hydrophobic interactions Disulfide-bonds Absolutely required for a protein to be active. Two main types of tertiary structures exist: Fibrous (e.g. collagen) Globular (e.g. myoglobin) Collagen myoglobin Tertiary structure CHMI 2227 - E.R. Gauthier, Ph.D.

  4. For proteins in an aqueous environment: Hydrophobic amino acids are buried in the interior of the structure; Hydrophilic amino acids are exposed to the solvent; Conversely, membrane-bound proteins are exposed to an hydrophobic environment: Hydrophobic amino acids are exposed; Hydrophilic amino acids are buried inside. http://butane.chem.uiuc.edu/cyerkes/chem104A_S07/Lecture_Notes_104/lect28c.html Tertiary structureInteraction forces CHMI 2227 - E.R. Gauthier, Ph.D. Check this one out: http://www.elmhurst.edu/~chm/vchembook/567tertprotein.html

  5. Protein folding occurs in specific steps: Some individual elements of secondary structure are first formed; A few elements of secondary structure cluster together to form conserved folding motifs; These bundles of secondary structure then form domains, which fold independently of the rest of the protein; Finally, several domains interact to form the final, functional 3-D structure of the protein. Any given protein will always adopt the same functional 3-D structure. Tertiary structure A B CHMI 2227 - E.R. Gauthier, Ph.D.

  6. Tertiary structureFolding motifs - 1 CHMI 2227 - E.R. Gauthier, Ph.D.

  7. Tertiary structureFolding motifs - 2 CHMI 2227 - E.R. Gauthier, Ph.D.

  8. Domain 1 Domain 2 Domain 3 Tertiary structureProtein domains – Pyruvate kinase CHMI 2227 - E.R. Gauthier, Ph.D.

  9. Found in muscles Binds the oxygen required for aerobic metabolism; Associated with a heme group, which is actually responsible for binding oxygen; b-turn b-turn Proline Tertiary structure1. Myoglobin CHMI 2227 - E.R. Gauthier, Ph.D.

  10. Hydrophilic amino acids: Blue Hydrophobic amino acids: Yellow Cross-sectional view Tertiary structure1. Myoglobin CHMI 2227 - E.R. Gauthier, Ph.D.

  11. Hydrophilic amino acids: Blue Hydrophobic amino acids: Yellow Tertiary structure2. Porin – a membrane-bound protein CHMI 2227 - E.R. Gauthier, Ph.D.

  12. Tertiary structureChaperones • For some proteins, folding requires the help of other proteins called chaperones; • Chaperones generally work by binding to exposed hydrophobic patches on the unfolded protein, preventing aggregation and irreversible inactivation. CHMI 2227 - E.R. Gauthier, Ph.D.

  13. Proteins can be denatured by treatments that destroy the interaction forces required for the adoption of the proper 3-D structure: Heat pH Solvent Urea/guadinium: breaks up H-bonds b-ME Tertiary structureProtein denaturation CHMI 2227 - E.R. Gauthier, Ph.D. Check this one out: http://www.elmhurst.edu/~chm/vchembook/568denaturation.html

  14. The fact that ribonuclease can be reversibly denatured and renatured in vitro shows that the information required for the proper folding of a protein resides in its primary structure. Tertiary structureProtein denaturation CHMI 2227 - E.R. Gauthier, Ph.D.

  15. Protein found in the jelly fish; Has the unique property to emit a green light; Different variants were produced by genetic engineering to produce red, yellow, cyan, blue light. Extremely useful in cell biology: one can tag it to her/his protein of interest and follow the protein in the cell using fluorescence microscopy. Examples of proteins1. Green fluorescent protein CHMI 2227 - E.R. Gauthier, Ph.D.

  16. Light! Examples of proteins1. Green fluorescent protein CHMI 2227 - E.R. Gauthier, Ph.D.

  17. Golgi apparatus Nucleus Examples of proteins1. Green fluorescent protein CHMI 2227 - E.R. Gauthier, Ph.D.

  18. Examples of proteins1. Green fluorescent protein CHMI 2227 - E.R. Gauthier, Ph.D.

  19. Toxic form = PrPsc http://en.wikipedia.org/wiki/Image:Prion.gif Normal form = PrPc Examples of proteins2. Prion proteins CHMI 2227 - E.R. Gauthier, Ph.D.

  20. Examples of proteins2. Prion proteins Fiber aggregation CHMI 2227 - E.R. Gauthier, Ph.D.

  21. Important web site:http://www.pdb.org/pdb/home/home.do CHMI 2227 - E.R. Gauthier, Ph.D.

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