passages.id: split_4_test_31_passage
passages.type: progene_text
passages.text: Overall the crystal structure of a monomer of the Oct-1 POU domain bound to the octamer element was similar to that predicted by the NMR solution structures of the POU - specific domain and the POU - homeodomain in isolation , with the POU - specific domain consists of four alpha helices , with the second and third helices forming a structure similar to the helix - turn - helix motif of the lambda and 434 repressors ; several of the DNA base contacts are also conserved .