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Forkhead-associated domain
In molecular biology, the forkhead-associated domain (FHA domain) is a phosphopeptide recognition domain found in many regulatory proteins.[1] It displays specificity for phosphothreonine-containing epitopes but will also recognise phosphotyrosine with relatively high affinity. It spans approximately 80-100 amino acid residues folded into an 11-stranded beta sandwich, which sometimes contains small helical insertions between the loops connecting the strands.[2] To date, genes encoding FHA-containing proteins have been identified in eubacterial, eukaryotic and archaeal genomes. The domain is present in a diverse range of proteins, such as kinases, phosphatases, kinesins, transcription factors, RNA-binding proteins, and metabolic enzymes which partake in many different cellular processes - DNA repair, signal transduction, vesicular transport, and protein degradation are just a few examples. DNA repairThe forkhead associated (FHA) domain of polynucleotide kinase phosphatase (PNKP) is necessary for the recruitment of PNKP to damage sites in DNA.[3] PNKP is active in the repair of DNA damage by the processes of base excision repair, single-strand break repair, and non-homologous end joining in the case of double strand breaks.[3] In these activities, PNKP acts both as a kinase and a phosphatase in the ligation of DNA ends. The kinase domain phosphorylates 5' hydroxyl ends, and the phosphatase domain removes phosphates from 3' ends. These activities, acting together, prepare single-strand breaks with damaged termini for ligation. References
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