Pur-alpha, the first sequence-specific single-stranded DNA-binding protein, belongs to the four-member Pur protein family; wherein, Pur protein sequences from bacteria through humans contain an amino acid segment that is strongly conserved.
Pur-alpha was the first sequence-specific single-stranded DNA-binding protein to be discovered in higher organisms (GenBank M96684.1; GI:190749). Pur-alpha belongs to the four-member Pur protein family, which also includes Pur-beta (GenBank AY039216.1; GI:14906267) and two forms of Purgamma (Variant A, GenBank AF195513.2; Variant B, GenBank AY077841). Pur protein sequences from bacteria through humans contain an amino acid segment that is strongly conserved (see NCBI ). 
