This entry represents HEAT repeats from Huntingtin (HTT), which are part of the N-terminal HEAT domain. These are a second set, separated from N-HEAT_1 (Pfam:PF20926) by an unstructured region [1,2]. HTT is expressed in many tissues with various expression levels and is involved in a number of cellular functions. However, its exact function is not yet clear. An abnormal polyglutamine (polyQ) expansion in this protein causes Huntington's disease (HD) a progressive autosomal-dominant neurodegenerative disease characterised by an uncontrolled motor movement known as chorea, cognitive disorder and depression [1]. HTT consists of multiple HEAT repeats organised in N-terminal, bridge and C-terminal domains [1], which function as a scaffold that mediated interactions with binding partners.

1: Cellular localization of the Huntington's disease protein and discrimination of the normal and mutated form. Trottier Y, Devys D, Imbert G, Saudou F, An I, Lutz Y, Weber C, Agid Y, Hirsch EC, Mandel JL; Nat Genet. 1995;10:104-110. PMID:7647777

2: The cryo-electron microscopy structure of huntingtin. Guo Q, Bin Huang, Cheng J, Seefelder M, Engler T, Pfeifer G, Oeckl P, Otto M, Moser F, Maurer M, Pautsch A, Baumeister W, Fernandez-Busnadiego R, Kochanek S; Nature. 2018;555:117-120. PMID:29466333

3: The Polyglutamine Expansion at the N-Terminal of Huntingtin Protein Modulates the Dynamic Configuration and Phosphorylation of the C-Terminal HEAT Domain. Jung T, Shin B, Tamo G, Kim H, Vijayvargia R, Leitner A, Marcaida MJ, Astorga-Wells J, Jung R, Aebersold R, Peraro MD, Hebert H, Seong IS, Song JJ; Structure. 2020;28:1035-1050. PMID:32668197