Figure 1

Multiple sequence alignment of archaeal primase CTDs and archaeal and eukaryotic GINS B-domains. The multiple sequence alignment of PriS CTD and archaeal GINS B-domains was generated using Clustal X 2.0 [28, 29] with default parameters. Sequences are denoted by their species names (left) and numeric Genbank Identifiers (GI numbers, right). The positions of the first and last residues of the aligned region of the corresponding protein are indicated. The colouring is based on the consensus shown underneath the alignment. Hydrophobic positions (ACFILMVWYH) are indicated by the letter h and shaded yellow when present in 80% of the sequences shown; small residues (ACDGNPSTV) are indicated by the letter s and shaded green. The secondary structure of the CTD of the S. solfataricus PriS protein (PDB code 1TZ2) is shown underneath the alignment (with H, E and L indicating α-helix, β-strand and loop regions respectively, with α-helices shown in red and β-strands in blue), as are the primary sequences and secondary structures of the B-domains of three of the four human GINS proteins: Sld5, Psf2 and Psf3 (derived from PDB file 2E9X). The alignment of the human GINS and S. solfataricus PriS CTD sequences was generated by pairwise structure comparison (1ZT2 versus 2E9X with default parameters) using DaliLite [27]. The inverted triangles above the Sld5 and Psf3 sequences indicate that amino acids have been omitted at these positions; the number of amino acids omitted is shown.