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. 2000 Oct 15;14(20):2623–2634. doi: 10.1101/gad.831900

Figure 1.

Figure 1

Conservation and domain structure of the Drosophila melanogaster Spt5 and Spt6 proteins. Overall regions of homology indicated by dashed lines. (A) Drosophila Spt5 domain structure illustrated with murine Spt5 as a comparison. Spt5 proteins have acidic amino termini (region B), sequence homology to Escherichia coli NusG (region C) (Hartzog et al. 1998; Wada et al. 1998a; Wu-Baer et al. 1998), and serine-, threonine-, and proline-rich carboxy-terminal repeat regions noted in Yamaguchi et al. (1999b) and defined as CTR1 and CTR2 in Stachora et al. (1997) (regions D and E). Region E of Drosophila Spt5 has characteristics of CTR1 and CTR2 but the repeats appear degenerate. Homology of D. melanogaster Spt5 determined by BLAST (Altschul et al. 1990) with murine Spt5 is 50% amino-acid identity (E value = 0.0) and with Saccharomyces cerevisiae is 26% amino-acid identity (E value = 1e-58). The amino-terminal RS domain of D. melanogaster (region A) is novel for the Spt5 proteins. (B) D. melanogaster Spt6 domain structure illustrated with murine Spt6 as a comparison. Like Spt5 proteins, Spt6 proteins have acidic amino-termini (region A). Spt6 proteins also have sequence homology with a prokaryotic family of proteins implicated in transcription regulation (region B, named after the Bordetella pertussis Tex protein (Fuchs et al. 1996) and this region contains a conserved helix–hairpin–helix fold (HhH, region C, [Doherty et al. 1996]). Most Spt6 proteins are also predicted to contain RNA-binding S1 domains (region D, [Bycroft et al. 1997]). All Spt6 proteins except S. cerevisiae Spt6 have extended, divergent carboxyl termini rich in certain amino acids such as serine, threonine, and glycine (Drosophila) or glutamine (mouse) (region E and data not shown). Homology (by BLAST) of D. melanogaster Spt6 with murine Spt6 is 48% amino-acid identity (E value = 0.0) and S. cerevisiae Spt6 is 22% amino-acid identity (E value = 3e-79).