<p>Phosphatidylinositol 3-kinase (PI3-kinase) (<db_xref db="EC" dbkey="2.7.1.137"/>) is an enzyme that phosphorylates phosphoinositides on the 3-hydroxyl group of the inositol ring. The usually N-terminal C2 domain interacts mainly with the scaffolding helical domain of the enzyme, and exhibits only minor interactions with the catalytic domain [<cite idref="PUB00007087"/>]. The domain consists of two four-stranded antiparallel beta-sheets that form a beta-sandwich. Isolated C2 domain binds multilamellar phospholipid vesicles which suggests that this domain could play a role in membrane association. Membrane attachment by C2 domains is typically mediated by the loops connecting beta-strand regions that in other C2 domain-containing proteins are calcium-binding region</p>