MolSlides.ProteinExplorer.Org

Start or Spacebar for First Slide.
Copyright © 2007 by Karl Oberholser,
Messiah College, Grantham, PA USA.

Permission is hereby granted to use this document, or portions thereof, for non-profit educational purposes, provided this copyright statement remains intact within this document, or any portions or derivatives. Other uses require explicit permission from the author(s).
Please Note: When MolSlides are exported to Jmol by this version of Protein Explorer, the molecular views may not always be faithful to the originals in Protein Explorer. We expect to correct this in future releases of Protein Explorer. If the renderings in Jmol are not satisfactory, please export your MolSlides to Chime. Also, please email to us your MolSlides to help us find and fix these issues.
A 1024 x 768 pixel window in a browser with current java is required for correct display of the MolSlides below. Viewing Help, Downloading, & Troubleshooting.. (at bottom).
Spacebar/Enter for next slide, Backspace for previous. More keystrokes.. (at bottom)
1 Next Bottom 2 3 4 5 6 7 8 9 Made with MolSlides.ProteinExplorer.Org

Coiled-coil Motif
A coiled-coil or superhelix is formed by coiling two, three or four a helices together. The helical strands are held together by the hydrophobic force formed between nonpolar side chains from the different peptide strands. A heptad repeat pattern of hydrophobic residues in the primary structure consistently bring these nonpolar side chains together every seventh residue. These nonpolar residues from different strands are properly located to interact with one another because the helix is slightly distorted by being less tightly wound than the normal a helix so that it has a pitch of 0.51 instead of 0.54 and there are 3.5 residues per turn instead of 3.6. With this slight left-handed twist to the right-handed a helix, there are exactly seven residues per two turns (2 x 3.5) in the distorted a helix, and therefore the side chains of the heptad residues are in place to interact with each other. (1)

This series of slides illustrates how the side chains of the heptad repeats align and gives examples of the coiled-coil motif.

Reference
1. Biochemistry, 3rd ed., R. H. Garrett & C. M. Grisham, Thomson/Brooks/Cole, page 181.

Made with MolSlides.ProteinExplorer.Org

2 Next Previous 1 3 4 5 6 7 8 9 View 1UO2 in ProteinExplorer.Org

Two Coiled Strands
GCN4 protein

Observe the slight coil in the strands.

Made with MolSlides.ProteinExplorer.Org

3 Next Previous 1 2 4 5 6 7 8 9 View 1UO2 in ProteinExplorer.Org

Two Coiled Strands
Heptad Repeat

Every seventh residue, shown in spacefill, in a chain is nonpolar, and with 3.5 residues per turn each heptad repeat is aligned with the one below and above it, as well as being in position to interact with the heptad repeat on a second strand.

Made with MolSlides.ProteinExplorer.Org

4 Next Previous 1 2 3 5 6 7 8 9 View 1UO2 in ProteinExplorer.Org

Two Coiled Strands
Looking down the spline of contact.

Made with MolSlides.ProteinExplorer.Org

5 Next Previous 1 2 3 4 6 7 8 9 View 1UO2 in ProteinExplorer.Org

Two Coiled Strands
The side chains of the residues located between the heptad repeats spiral around the helix away from the side chains on the partner strand, thus not permitting interactions between these side chains of the two strands.

Made with MolSlides.ProteinExplorer.Org

6 Next Previous 1 2 3 4 5 7 8 9 View 1HTM in ProteinExplorer.Org

Three Coiled Strands
Influenza Hemagglutinin - one of the viral proteins that is immunologically active

There are three peptide strands that form the coiled-coil.

Made with MolSlides.ProteinExplorer.Org

7 Next Previous 1 2 3 4 5 6 8 9 View 1HTM in ProteinExplorer.Org

Three Coiled Strands
The heptrad repeats of each strand are shown in spacefill.

Made with MolSlides.ProteinExplorer.Org

8 Next Previous 1 2 3 4 5 6 7 9 View 1G6N in ProteinExplorer.Org

Coiled-Coils in Globular Protein
Catabolite Activator Protein (CAP) - a globular protein that is an important regulator of several aspects of catabolism

Notice the two coiled a helices in the center of the structure. Each coil is a part of a different subunit, and the formation of the coiled-coil plays a pivotal role in holding the two subunits together.

Made with MolSlides.ProteinExplorer.Org

9 LAST VIEW Previous Top 1 2 3 4 5 6 7 8 View 1G6N in ProteinExplorer.Org

Coiled-Coils in Globular Proteins
CAP

The heptrad repeats are shown in spacefill.

Made with MolSlides.ProteinExplorer.Org

Made with MolSlides.ProteinExplorer.Org

Viewing Help Downloading Help Troubleshooting

Viewing Help for MolSlides:

Here are the recommended browsers.
Maximize your window, then View, Full Screen (F11).
For a small (800 x 600 pixel) window, reduce the text size (View, Text Size). Then Reload the MolSlides.
Keystroke controls (not all work in every browser, but the links above each slide Next, Previous, 1, 2, ... 9 always work.):
- Next Slide: Spacebar, Enter, Down Arrow, Right Arrow, PgDn.
- Previous Slide: Backspace, Up Arrow, Left Arrow, PgUp.
- Slide Number: 1-9.
- First Slide: Home, Esc.
- Last Slide: End.

Download These MolSlides

Please respect the copyright statement, if any is present in these MolSlides.
Make a new folder (directory) to receive your MolSlides.
Save the MolSlides themselves with your browser's File, Save As. (Some browsers may not save the MolSlides correctly. On Windows, these browsers are known to work well: Firefox, Netscape 7.2, Mozilla.)
Save each PDB file needed by this set of MolSlides (see list below under Troubleshooting). Click on the Jmol frank at the lower right corner of each molecular view, and choose the top item on the menu, a 4-character "PDB ID code". On the submenu, choose the bottom item, a code plus ".pdb". If a black browser window opens showing a wireframe rendering of the molecule (in MDL Chime), click on the MDL frank at the lower right corner and choose File, Save Molecule As.
You will also need the files JmolApplet.jar, JmolApplet0.jar, ... JmolApplet6.jar available from Jmol Download.
Double-click on the MolSlides HTML file to view it, or drag and drop it onto or into the browser you wish to use.

Troubleshooting MolSlides:

Can't see the molecule(s)?

This set of MolSlides uses the Jmol java applet, which requires Java on your computer. Some Windows computers need java (free) installed from java.com. (Also, the folder/directory supplying this MolSlides file must contain the JmolApplet#.jar files.)
If some (or all) slides have blank rectangles without any molecules, some (or all) of the necessary PDB files may be missing from the folder (directory) supplying this MolSlides file. This set of MolSlides needs the following PDB files:
1UO2.pdb, 1HTM.pdb, 1G6N.pdb