C1 domain

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C1 domain of PKC-delta (1ptr) Middle plane of the lipid bilayer - black dots. Boundary of the hydrocarbon core region - blue dots (cytoplasmic side). Layer of lipid phosphates - yellow dots.

C1 domain (also knowbn as phorbol esters/diacylglycerol binding domain) binds an important secondary messenger diacylglycerol (DAG) and phorbol esters.

Phorbol esters (such as PMA) are analogues of DAG and potent tumor promoters that cause a variety of physiological changes when administered to both cells and tissues. DAG activates a family of serine/threonine protein kinases, collectively known as protein kinase C (PKC). Phorbol esters can directly stimulate PKC.

The N-terminal region of PKC, known as C1, binds PMA and DAG in a phospholipid and zinc-dependent fashion. The C1 region contains one or two copies of a cysteine-rich domain, which is about 50 amino-acid residues long, and which is essential for DAG/PMA-binding.

The DAG/PMA-binding domain binds two zinc ions; the ligands of these metal ions are probably the six cysteines and two histidines that are conserved in this domain.