Introduction - Proteins have a limited number of structural motifs.
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This is a common secondary structure in proteins - the
HELIX-LOOP-HELIX
motif.
This helix-loop-helix motif is called the "EF HAND" and represents the
CALCIUM
-binding motif in many calcium-binding proteins (based on 5CPV.pdb, Swain,
Kretsinger & Amma J. Biol. Chem 264 16620 (1989)).
The calcium ion is bound to two Asp side chains and a Glu side chain.
This is a HAIRPIN BETA-SHEET motif. Note that
the β-strands are anti-parallel (direction of the arrows).
This is the BETA-ALPHA-BETA motif. Note that
the β-strands are parallel (direction of the arrows).