Claim: Pur-alpha, the first sequence-specific double-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.
Evidence: Pur-alpha was the first sequence-specific single-stranded DNA-binding protein to be discovered in higher organisms (GenBank M96684.1; GI:190749).