Sandbox 213: Difference between revisions
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The calmodulin structure has been determined by NMR. This method reveals that calmodulin is a long molecule which looks like a '''dumbbell''' because it contains '''two globular domains''' (the <scene name='Sandbox_213/N-lobe/1'>N-lobe</scene> and the <scene name='Sandbox_213/C-lobe/1'>C-lobe</scene>) linked by a <scene name='Sandbox_213/flexible α-helix/1'>flexible α-helix</scene>. | The calmodulin structure has been determined by NMR. This method reveals that calmodulin is a long molecule which looks like a '''dumbbell''' because it contains '''two globular domains''' (the <scene name='Sandbox_213/N-lobe/1'>N-lobe</scene> and the <scene name='Sandbox_213/C-lobe/1'>C-lobe</scene>) linked by a <scene name='Sandbox_213/flexible α-helix/1'>flexible α-helix</scene>. | ||
Each lobe contains a pair of <scene name='Sandbox_213/helix-loop-helix/1'>helix-loop-helix</scene> motifs (called EF-hand) that can bind two Ca<sup>2+</sup> ions. However those lobes do not have the same properties because the C-lobe has higher Ca<sup>2+</sup> affinity than the N-lobe. | Each lobe contains a pair of <scene name='Sandbox_213/helix-loop-helix/1'>helix-loop-helix</scene> motifs (called EF-hand or calmodulin-fold) that can bind two Ca<sup>2+</sup> ions. However those lobes do not have the same properties because the C-lobe has higher Ca<sup>2+</sup> affinity than the N-lobe. | ||
The two EF-hands are located in the vicinity of each other. Those neighboring sited are very likely to structurally influence each other upon Ca<sup>2+</sup> binding to one of them. | The two EF-hands are located in the vicinity of each other. Those neighboring sited are very likely to structurally influence each other upon Ca<sup>2+</sup> binding to one of them. | ||
A superfamily of proteins utilizes the configuration of helix-loop-helix to bind Ca<sup>2+</sup> but calmodulin is the only member that subserves so many functions. | |||
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*'''Ca<sup>2+</sup>-bound calmodulin''' | *'''Ca<sup>2+</sup>-bound calmodulin''' | ||
Calmodulin uses a linear sequence of 12 amino acids to bind Ca<sup>2+</sup>. | |||
Binding of Ca<sup>2+</sup> to the four sites induces a large conformational change causing the terminal helices to expose hydrophobic surfaces and also a long central α-helical segment. Ca<sup>2+</sup>-bound calmodulin binds to its targets with high affinity (K<sub>D</sub>≈10<sup>−9</sup> mol.L<sup>−1</sup>). | Binding of Ca<sup>2+</sup> to the four sites induces a large conformational change causing the terminal helices to expose hydrophobic surfaces and also a long central α-helical segment. Ca<sup>2+</sup>-bound calmodulin binds to its targets with high affinity (K<sub>D</sub>≈10<sup>−9</sup> mol.L<sup>−1</sup>). | ||
