QUATERNary Structures and Denaturing of

ProteinsChapter 14.11- 14.12

Quaternary Structure

- The highest level of protein organization, Quaternary Structure, refers to proteins with more than one polypeptide chain.

- Broken up into Subunits:1. Hemoglobin2. Collagen3. Integral Membrane Proteins

Hemoglobin

• Made up of 4 chains, called “Globins”• 2 α chains of 141 amino acid

residues.• 2 β chains of 146 amino acid

residues.• Each Globin Chain encompasses an

iron-containing heme unit.• Conjugated Proteins- Proteins that

contain non-amino acid portions.• Prosthetic Group- The non-amino acid

of a protein.

Hemoglobin: The Revenge

• Hemoglobin is not merely separated into the two aforementioned groups.

• As a fetus our Hemoglobin has a greater affinity for oxygen than as a born human.

• This is because the mother supplies the blood for the fetus.

• This also helps eliminate symptoms of Cell Anemia.

Collagen

A grand example of another quaternary structures in proteins.

Constituted by triple helix units called tropocollagen!

After a long time, they become insoluble.

Cross-linking allows helixes to connect and creates the stabilized formation of proteins structures.

Integral Membrane Proteins

Traverse a protein layer either partly or completely.33.3333% of proteins are estimated to be Integral

Membrane Proteins.This allows polar proteins to remain stable in a non-polar

environment.2 Quaternary Structures:

+ 6 to 10 α-helices crossing the membrane + β-barrels 8, 12, 16 or 18 antiparallel sheets.

Denaturation of Proteins

• Denaturation- the process of the loss of a secondary, tertiary, or quaternary proteins through the use of a chemical or physical agent.

• Agents of Denaturation: Heat, 6m Urea, Detergents, Acids/bases, Salts, Reducing Agents, Heavy Metals, and Alcohol.

• Each Denaturation Agent affects a different part of the protein!

• The Denaturation Process is the process that happens when one boils an egg.

Collagen 2: The Sequel

• Reducing agents can…reduce… -S-S- bonds to form –SH groups.

• This is what makes your hair curly I with a straightener.

• Heavy Metal ions form salt bridges which denatures milk and eggs.

• Denaturing also sterilizes skin before injections.• Denaturing is reversible if the changes are

minimal.