User:Alice Harmon/EF Hand

EF-hands are calcium-binding motifs found in hundreds of proteins. They bind calcium ions with high affinity (K_ds are in the micromolar range) and selectivity, and this property allows EF-hand proteins to sense changes in intracellular calcium. In unstimulated cells cellular free calcium concentrations [Ca²⁺]_c are in the nanomolar range (~10 nM in animal cells and ~200 nM in plant cells), and EF-hands are generally unoccupied by Ca²⁺. Upon stimulation, Ca²⁺ enters the cytosol from either outside the cell or from internal organelles, and [Ca²⁺]_c rises to the micromolar range. EF-hands bind Ca²⁺, and this binding causes a conformational change that alters the activity of the protein.

The name EF-hand originated from the first such structure to be described, which was in the protein parvalbumin. In this protein calcium is bound by a helix-loop-helix structure that is formed by the E and F helices (letters assigned to helices in the order that they occur starting at the N-terminus). See the annotated protein sequence for carp parvalbumin here [1].

Below are EF-hands found in parvalbumin, calmodulin, and calcium-dependent protein kinase.

spinqualitylabelsall models 3hx4 - active TgCDPK1 Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image 3HX4

spinqualitylabelsall models 1prw - Bovine calmodulin Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image 1prw

spinqualitylabelsall models 4cpv - Carp parvalbumin Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image 4cpv