Elements of Protein Structure

Interactions important in Maintaining Protein Structure

So far, in the previous module, We discussed only the fact that a protein is a polymer of amino acids. Indicated were only the bonds that make an amino acid and those that connect them into the polymer. What was also mentioned several times was that proteins do not have a random three dimensional structure but that each kind of protein type has a specific sequnce of amino acids and that this sequence determines how it folds in three dimensions. Every molecule that has the same sequence has an "identical" 3-D shape.

This shape is maintained solely by the physical interactions between molecules within the protein as well as between the molecules of the protein its surrounding solvent. These interaction fall into several types of classifications:

• Steric interactions.
• Ionic interactions
• polar interactions
• Hydrogen bonds ( a special case of polar interaction)
• Van DerWaals Interactions
• Hydrophobic interaction (or lack of interaction as the case may be)
• Inter-amino acid sidechain covalent bonds

In the next several pages we will discuss each of these in turn, what is their role, their relative importance and where we would expect to find them within the protein structure.