C2-domains, Structure and Function of a Universal Ca2+-binding Domain
A vast amount of protein sequence data accumulated over recent years has revealed that protein modules are widespread in nature. Many intracellular and extracellular proteins consist, in part or fully, of combinations of protein modules. C2-domains, together with SH2, PTB, PH, SH3, WW, and PDZ domains, are typical examples of intracellular protein modules. These modules form independently folding domains of 80–160 residues with characteristic binding properties; C2-domains bind Ca2+ and phospholipids, SH2 and PTB domains phosphotyrosine-containing sequences, PH domains phosphatidylinositol phosphates, SH3 and WW domains proline-rich sequences, and PDZ domains C-terminal sequences.