Domain architecture and sequence alignment of Nanos. (A) Domain architecture of zebrafish Nanos composed of 159 amino-acid residues. The two CCHC zinc-finger motifs, ZF1 and ZF2, are indicated. (B) Sequence alignment of the zinc-finger domain of Nanos from zebrafish (z), mouse (m) and Drosophila melanogaster (dm). Identical and homologous residues are highlighted by a black and grey background, respectively. The CCHC motifs in ZF1 and ZF2 are highlighted by a pink and purple background, respectively. The secondary structure of zNanos is also shown above the sequence. Missense mutations causing an abdominal or oogenesis nanos phenotype in Drosophila are shown below the sequence (Arrizabalaga & Lehmann, 1999). CCHC, Cys-Cys-His-Cys; ZF, zinc-finger.