This is a helix-loop-helix, calcium-binding motif, in which two helices pack together at an angle of approximately 90 degrees, separated by a loop region, where calcium binds. The 'EF' notation for the motif resulted from the structure of parvalbumin, in which the 'E' and 'F' helices were originally identified to form this calcium-binding motif. The example shown is a human psoriasin (PDB code 1psr).
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