The HAT (Half A TPR) repeat has a repetitive pattern characterised by three aromatic residues with a conserved spacing. They are structurally and sequentially similar to TPRs (tetratricopeptide repeats), though they lack the highly conserved alanine and glycine residues found in TPRs. The number of HAT repeats found in different proteins varies between 9 and 12. HAT-repeat-containing proteins appear to be components of macromolecular complexes that are required for RNA processing [1]. The repeats may be involved in protein-protein interactions. The HAT motif has striking structural similarities to HEAT repeats (IPR000357), being of a similar length and consisting of two short helices connected by a loop domain, as in HEAT repeats.
Bai Y, Auperin TC, Chou CY, Chang GG, Manley JL, Tong L.
Crystal structure of murine CstF-77: dimeric association and implications for polyadenylation of mRNA precursors.
Mol. Cell 25 2007 863-75
[PubMed: 17386263] http://dx.doi.org/10.1016/j.molcel.2007.01.034