Domain structure diagram of FhkA and CBP4a. (A) FhkA (Rad53 in yeast, Chk2 in humans) possesses several putative FHA domains (asterisk indicates verified domains [47, 48]). Putative NLSs and the antigen site for anti-FhkA are indicated. Numbers represent amino acid position. Western blot shows the detection of FhkA by anti-FhkA at ~70 kDa as well as the absence of FhkA detection by the preimmune serum. (B) CBP4a possesses a putative FHA domain and putative NLS as well as four EF-hand Ca2+-binding motifs. The antigen site is shown for both FhkA and CBP4a.