The forkhead-associated (FHA) domain was originally described as a small domain in transcription factors with forkhead-type DNA binding domains. More recently, FHA domains have also been identified in protein kinases and other proteins that are not transcription factors such that most of the proteins now known to contain FHA domains function in cell cycle control. Biochemical and structural studies suggest that FHA domains are protein-protein interaction domains with specificity for phosphorylated targets. The structural studies have focused on the two FHA domains present within Rad53, a budding yeast DNA damage checkpoint kinase. Three-dimensional structures of the N-terminal FHA domain (N-FHA) bound to a phosphothreonine-containing peptide and of the C-terminal FHA domain (C-FHA) bound to a phosphotyrosine-containing peptide have been determined by crystallography and NMR, respectively, and show overall similar folds for the two FHA domains.

Reference:

1. E. S. Stavridi, Y. Huyen, I. R. Loreto, D. M. Scolnick, T. D. Halazonetis, N. P. Pavletich, P. D. Jeffrey, Crystal structure of the FHA domain of the Chfr mitotic checkpoint protein and its complex with tungstate. Structure 10, 891 (2002).

The family is the synonymous family of FHA in PlnTFDB.