This family consists of several progressive ankylosis protein (ANK or ANKH) sequences. The ANK protein spans the outer cell membrane and shuttles inorganic pyrophosphate (PPi), a major inhibitor of physiologic and pathologic calcification, bone mineralisation and bone resorption [1]. Mutations in ANK are thought to give rise to Craniometaphyseal dysplasia (CMD) which is a rare skeletal disorder characterised by progressive thickening and increased mineral density of craniofacial bones and abnormally developed metaphyses in long bones [2]. This family shows distant homology to the MOP (TCDB) superfamily of transporters.

1: Heterozygous mutations in ANKH, the human ortholog of the mouse progressive ankylosis gene, result in craniometaphyseal dysplasia. Nurnberg P, Thiele H, Chandler D, Hohne W, Cunningham ML, Ritter H, Leschik G, Uhlmann K, Mischung C, Harrop K, Goldblatt J, Borochowitz ZU, Kotzot D, Westermann F, Mundlos S, Braun HS, Laing N, Tinschert S; Nat Genet 2001;28:37-41. PMID:11326272

2: Autosomal dominant craniometaphyseal dysplasia is caused by mutations in the transmembrane protein ANK. Reichenberger E, Tiziani V, Watanabe S, Park L, Ueki Y, Santanna C, Baur ST, Shiang R, Grange DK, Beighton P, Gardner J, Hamersma H, Sellars S, Ramesar R, Lidral AC, Sommer A, Raposo do Amaral CM, Gorlin RJ, Mulliken JB, Olsen BR; Am J Hum Genet 2001;68:1321-1326. PMID:11326338