Figure 2.—

The SF2 helicase Mus301 is a member of the Mus308 subfamily. (A) The genomic structure of mus301 (CG7972); boxes represent exons; shaded boxes indicate conserved motifs of SF2 helicases. Mus301 possesses nine conserved motifs characteristic of SF2 helicases, and motif IVa, present in the Mus308 subfamily of helicases. The Q motif is split between exons 1 and 2. The rest of the motifs are contained in exons 2, 3, and 4. The molecular lesions identified in six mus301 mutant alleles are shown. Missense amino acid substitutions or base changes and allele numbers (in parentheses) are indicated. The solid box represents the 3′-UTR. (B) Alignment of the helicase domains of D. melanogaster Mus301 and Mus308 and human HEL308. Open arrowheads indicate the conserved G and Q residues of the Q motif; asterisks denote the unique amino acid variations found in the Mus308 subfamily of helicases.