Protein kinase C conserved region 1 (C1) . Cysteine-rich zinc binding domain. Some members of this domain family bind phorbol esters and diacylglycerol, some are reported to bind RasGTP. May occur in tandem arrangement. Diacylglycerol (DAG) is a second messenger, released by activation of Phospholipase D. Phorbol Esters (PE) can act as analogues of DAG and mimic its downstream effects in, for example, tumor promotion. Protein Kinases C are activated by DAG/PE, this activation is mediated by their N-terminal conserved region (C1). DAG/PE binding may be phospholipid dependent. C1 domains may also mediate DAG/PE signals in chimaerins (a family of Rac GTPase activating proteins), RasGRPs (exchange factors for Ras/Rap1), and Munc13 isoforms (scaffolding proteins involved in exocytosis).