Biomolecules:
Proteins 2
Home
Table of Contents
Biomolecules Gateway Page
Jmol Tutorial

In this module:

Introduction
Secondary Structure
a Helices
ß Sheets
Motifs
Tertiary Structure
Disulfide Bonds, Domains
Cofactors, Quaternary Structure
Protein Folding
Alzheimer's and "Mad-Cow" Diseases

Tertiary Structure: Water-Soluble Proteins

Although the dividing line between them is somewhat vague, tertiary structure is distinguished from secondary structure by the fact that it describes the relationship between atoms far removed in the amino acid sequence. The tertiary structure is how a helices, ß sheets, other secondary structure elements, and motifs come together to form the overall structure of the protein.

Two general kinds of proteins are found in cells, water soluble and water insoluble proteins. Water soluble proteins, which include enzymes and transport proteins, are found free in cellular compartments such as the cytoplasm, nucleus, or endoplasmic reticulum. How do secondary structure elements come together to form the tertiary structure of water-soluble proteins?

* These structures use the slab mode to explore the interior of the protein.

Tertiary Structure: Water-Insoluble Proteins

The other class of proteins is not water-soluble. This include proteins that cross lipid bilayers once or more (integral membrane proteins). (See the Lipids module for a discussion of lipid bilayers.) Integral membrane proteins include membrane channels, pumps, and receptors. The portions that cross the bilayer are often a helices or ß sheets. Click on the buttons below to see why.

In membrane-spanning ß sheets, every other side chain faces the lipids and is usually hydrophobic.

Tertiary Structure