3D Structure of Calmodulin

On this page, you can see a 3D structure of calmodulin (with Ca ions already bound). There are some useful tools below in order to aid in your understanding of calmodulin's structure and function. Please reference previous webpages for more background information on the calmodulin protein.

Reset and spin this DNA molecule. The CPK coloring scheme was used here to represent all of the atoms in the calmodulin protein.

Look at the backbone of the calmodulin protein to gain a more general sense of EF domains separated by a central "linker" region.

Note that the calmodulin protein is one single amino acid strand as indicated by the existence of 1 red end (C-Terminus) and 1 blue end (N-Terminus).

Look at the spacefill with amino acids colored in order to grasp the visual dumbell shape of the calmodulin protein. The coloring scheme used here is the amino scheme, where each of the 20 amino acids is given a color which corelates to properties of that amino acid.

Look at the secondary structure, alpha helices are in pink and beta sheets are in yellow. Notice the existence of a long connecting alpha-helix (which is the protion of the protein that wraps around its target molecule).

Look at the 4 calcium ions in blue that bind to calmodulin at the 4 EF-hand motifs/domains. Recall that the binding of Ca ions activates calmodulin, allosterically modifying its shape.

Look at the central helix (in yellow) that connects the EF motifs (shown in cyan), where the Ca ions (shown in blue) bind. It is this central helix that acts as the "linker" sequence and allows for the flexibility of the calmodulin protein when bidning to various target molecules. The EF motifs where the Ca ions bind are positioned between two alpha helices as represented by the pink coloring scheme for the secondary structure of calmodulin.

Look at the Met amino acids (in blue) at the EF hands. These Met amino acids are hydrophobic and become exposed on the calmodulin protein only after the 4 Ca ions bind. The exposure of these hydrophobic regions is important for the ability of calmodulin to bind to various target molecules. Also note the location of these hydrophobic Met amino acids- they are within grooves of the protein, which is where the target molecule binds.

Out of all 148 amino acids in the primary amino acid sequence for calmodulin, only 3 amino acids differ between the bovine brain calmodulin sequence and the sea anemone calmodulin sequence. These 3 amino acids are highlighted in red. The small number of differences considering the evolutionarily distinct and distant species point to the fact that the calmodulin sequence is highly conserved (at least within the bovine and sea anemone) (Stevens, 1982).

Works Cited

Chattopadhyaya et al. Calmodulin Structure Refined at 1.7 Å Resolution. Journal of Molecular Biology 1992; 228: 1177-1192.

Nathan Silva and David Marcey. An Introduction to Jmol Scripting. Online posting 2007. Accessed 8 April 2010. Available from http://www.callutheran.edu/BioDev/omm/scripting/molmast.htm#V.

Stevens, F. C. Calmodulin: an introduction. Canadian Journal of Biochemistry and Cell Biology 1983; 61: 906-910.

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