HEAT repeat | |||||||||||
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![]() An example of an alpha solenoid structure composed of 15 HEAT repeats. The protein phosphatase 2A regulatory subunit is shown with the N-terminus in blue at bottom and the C-terminus in red at top. A single helix-turn-helix motif is shown in the center with the outer helix in pink, the inner helix in green, and the turn in white. From PDB: 2IAE . [1] [2] | |||||||||||
Identifiers | |||||||||||
Symbol | HEAT | ||||||||||
Pfam | PF02985 | ||||||||||
InterPro | IPR000357 | ||||||||||
PROSITE | PDOC50077 | ||||||||||
SCOP2 | 1b3u / SCOPe / SUPFAM | ||||||||||
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A HEAT repeat is a protein tandem repeat structural motif composed of two alpha helices linked by a short loop. HEAT repeats can form alpha solenoids, a type of solenoid protein domain found in a number of cytoplasmic proteins. The name "HEAT" is an acronym for four proteins in which this repeat structure is found: Huntingtin, elongation factor 3 (EF3), protein phosphatase 2A (PP2A), [3] and the yeast kinase TOR1. [4] HEAT repeats form extended superhelical structures which are often involved in intracellular transport; they are structurally related to armadillo repeats. The nuclear transport protein importin beta contains 19 HEAT repeats.
Representative examples of HEAT repeat proteins include importin β (also known as karyopherin β) family, [5] regulatory subunits of condensin and cohesin , [6] separase, [7] PIKKs (phosphatidylinositol 3-kinase-related protein kinases) such as ATM (Ataxia telangiectasia mutated) and ATR (Ataxia telangiectasia and Rad3 related), [8] [9] and the microtubule-binding protein XMAP215/Dis1/TOG [10] and CLASP. [11] Thus, cellular functions of HEAT repeat proteins are highly variable.
The structure of the following HEAT repeat proteins have been determined so far:
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