Figure 5

Homology model of the Thermoplasma acidophilum GINS homotetramer. (A) Structure-based sequence alignment of GINS subunits of Homo sapiens (Hs), Thermococcus kodakaraensis (Tk), and Thermoplasma acidophilum (Ta). Amino acid residues are colored according to their characteristics (aromatic, cyan; hydrophobic, green; basic, magenta; ambivalent, orange). Secondary structural elements are indicated on the top of the sequences. Numbering of α-helices and β-strands is according to the human GINS subunits [15]. (B) Two types of models in different conformations, the AB- and BA-types, are shown on the top and bottom, respectively. For the models, the A domain (residues 1 to 123, green in AB-type and blue in BA-type), the ID-loop (residues 124 to 172, white in both models), and the B domain (residues 173 to 233, red in AB-type and orange in BA-type) are differently colored. (C) A model of the TacGINS homotetramer. (D) Class averages of electron microscopic images of the TacGINS complex. The two-dimensional class averages of the EM images of the TacGINS complex (upper row). Similar projections (middle row) were obtained from the assumed atomic model. The atomic models of the TacGINS tetramer in the corresponding orientations are shown (lower row). The side length of the individual images in the upper and middle rows is 13.2 nm.