This entry represents the C-terminal domain of Huntingtin (Htt), which consists of HEAT repeats. 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 (Pfam:PF20926 and Pfam:PF12372), bridge (Pfam:PF20925) and C-terminal domains [1], which function as a scaffold that mediated interactions with binding partners. It has been suggested that the polyQ expansion in Htt alters phosphorylation status along the protein which affects its structure and function. In particular, modifications of phosphorylation in this domain induce conformational changes that impair its movement and interaction with the N-HEAT domain [2].

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