CCM2_HHD is a folded-helical region of a family of vertebral proteins, mutations in which cause cerebral cavernous malformations (CCMs). These malformations are congenital vascular anomalies of the central nervous system that can result in haemorrhagic stroke, seizures, recurrent headaches, and focal neurologic deficits [1]. This domain is structurally homologous to the N-terminal domain of harmonin, so it is named the CCM2 harmonin-homology domain or CCM2_HHD [2]. This protein is often called Malcavernin.

1: Mutations in a gene encoding a novel protein containing a phosphotyrosine-binding domain cause type 2 cerebral cavernous malformations. Liquori CL, Berg MJ, Siegel AM, Huang E, Zawistowski JS, Stoffer T, Verlaan D, Balogun F, Hughes L, Leedom TP, Plummer NW, Cannella M, Maglione V, Squitieri F, Johnson EW, Rouleau GA, Ptacek L, Marchuk DA; Am J Hum Genet. 2003;73:1459-1464. PMID:14624391

2: Structural studies of cerebral cavernous malformations 2 (CCM2) reveal a folded helical domain at its C-terminus. Fisher OS, Zhang R, Li X, Murphy JW, Demeler B, Boggon TJ; FEBS Lett. 2013;587:272-277. PMID:23266514