CHMI 2227 - E.R. Gauthier, Ph.D.*CHMI 2227EBiochemistry IProteins: Tertiary structure

CHMI 2227 - E.R. Gauthier, Ph.D.

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

CHMI 2227 - E.R. Gauthier, Ph.D.

CHMI 2227 - E.R. Gauthier, Ph.D.*Tertiary structureSecondary structure:Involves a single type of structure:a-helixb-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 bondsElectrostatic interactionsVan der Waals interactionsHydrophobic interactionsDisulfide-bonds

Absolutely required for a protein to be active.

Two main types of tertiary structures exist:Fibrous (e.g. collagen)Globular (e.g. myoglobin)

CHMI 2227 - E.R. Gauthier, Ph.D.

CHMI 2227 - E.R. Gauthier, Ph.D.*Tertiary structureInteraction forcesFor 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.Check this one out: http://www.elmhurst.edu/~chm/vchembook/567tertprotein.html

CHMI 2227 - E.R. Gauthier, Ph.D.

CHMI 2227 - E.R. Gauthier, Ph.D.*Tertiary structureProtein 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.AB

CHMI 2227 - E.R. Gauthier, Ph.D.

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

CHMI 2227 - E.R. Gauthier, Ph.D.

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

CHMI 2227 - E.R. Gauthier, Ph.D.

CHMI 2227 - E.R. Gauthier, Ph.D.*Tertiary structureProtein domains Pyruvate kinase

CHMI 2227 - E.R. Gauthier, Ph.D.

CHMI 2227 - E.R. Gauthier, Ph.D.*Tertiary structure1. MyoglobinFound in muscles

Binds the oxygen required for aerobic metabolism;

Associated with a heme group, which is actually responsible for binding oxygen;

CHMI 2227 - E.R. Gauthier, Ph.D.

CHMI 2227 - E.R. Gauthier, Ph.D.*Tertiary structure1. Myoglobin

CHMI 2227 - E.R. Gauthier, Ph.D.

CHMI 2227 - E.R. Gauthier, Ph.D.*Tertiary structure2. Porin a membrane-bound protein

CHMI 2227 - E.R. Gauthier, Ph.D.

CHMI 2227 - E.R. Gauthier, Ph.D.*Tertiary structureChaperonesFor 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.

CHMI 2227 - E.R. Gauthier, Ph.D.*Tertiary structureProtein denaturationProteins can be denatured by treatments that destroy the interaction forces required for the adoption of the proper 3-D structure:Heat pHSolventUrea/guadinium: breaks up H-bondsb-MECheck this one out: http://www.elmhurst.edu/~chm/vchembook/568denaturation.html

CHMI 2227 - E.R. Gauthier, Ph.D.

CHMI 2227 - E.R. Gauthier, Ph.D.*Tertiary structureProtein denaturationThe 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.

CHMI 2227 - E.R. Gauthier, Ph.D.

CHMI 2227 - E.R. Gauthier, Ph.D.*Examples of proteins1. Green fluorescent proteinProtein 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.

CHMI 2227 - E.R. Gauthier, Ph.D.

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

CHMI 2227 - E.R. Gauthier, Ph.D.

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

CHMI 2227 - E.R. Gauthier, Ph.D.

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

CHMI 2227 - E.R. Gauthier, Ph.D.

CHMI 2227 - E.R. Gauthier, Ph.D.*Examples of proteins2. Prion proteins

CHMI 2227 - E.R. Gauthier, Ph.D.

CHMI 2227 - E.R. Gauthier, Ph.D.*Examples of proteins2. Prion proteinsFiber aggregation

CHMI 2227 - E.R. Gauthier, Ph.D.

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

CHMI 2227 - E.R. Gauthier, Ph.D.