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 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 (represented in this entry) and C-terminal domains [1], which function as a scaffold that mediates interactions with binding partners. This domain connects the N- and C-HEAT domains.

1: 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

2: 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