Differences between the Apo and Calcium-Loaded States of Calmodulin N-terminal Domain

Analysis of the Conformational Differences between the Apo and Calcium-Loaded States of Calmodulin N-terminal Domains

A comparison of the conformations of the apo and calcium-loaded states of the N-terminal domain of calmodulin: Interhelical distance difference matrix (DDM) entries are shown in the left panels and interhelical contacts in the two states of CaM-N are shown in the center (apo) and right (calcium-loaded) panels. The DDM entries are mapped onto a ribbon representation of apo CaM-N. Residues that are moderately closer together in the apo state (DD between -2 and -5 angstroms) are connected by light blue lines. Residues that are much closer together in the apo state (DD less than -5 angstroms) are connected by dark blue lines. Residues that are moderately closer together in calcium-loaded state (DD between 2 and 5 angstroms) are connected by pink lines. Residues that are much closer together in the calcium-loaded state (DD greater than 5 angstroms) are connected by red lines. Interhelical contacts are categorized on the basis of the centers of geometry (CG) of the respective residues. Close contacts (distance between CGs less than 5 angstroms) are shown as purple lines, mid-range contacts (distance between CGs between 5 and 6.5 angstroms) are shown as blue lines, and long-range contacts (distance between CGs between 6.5 and 8 angstroms) are shown as green lines. Contacts unique to one state are shown as solid lines. Contacts found in both domains are shown as dotted lines. The helices were rendered as ribbons using InsightII (MSI, San Diego, CA), and the DDs and contacts were rendered as distance restraints using the NMR_Refine module of InsightII. PDB coordinates are: 1CLL (calcium-loaded calmodulin) and 1CFC (apo calmodulin).

The panels are: A) the helix I/II interface, B) the helix III/IV interface, C) the helix II/III interface, D) the helix I/IV interface, and E) the helix II/IV interface. Helices I and III do not contact in either of the sxtructures, and therefore a comparison of the interface between these two helices is not shown.

This graphic was figure 2 in the paper:
Nelson, M.R., W.J. Chazin. An Interaction-Based Analysis of Calcium-Induced Conformational Changes in Ca2+ Sensor Proteins (1998) Prot. Sci. 7, 270-282.

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