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Fig. 3 | Molecular Medicine

Fig. 3

From: Structural Basis of Bloom Syndrome (BS) Causing Mutations in the BLM Helicase Domain

Fig. 3

Structural model of BLM helicase domain. (A) Superimposition of ribbon diagrams of the template protein PcrA DNA helicase (3PJR) and the BLM helicase domain (yellow). The trace of the PcrA helicase from residues 4 to 652 and the structural model of the BLM protein from residues 655 to 1029 are shown. The PcrA DNA helicase is comprised of four subdomains 1A (magenta), 1B (green), 2A (red) and 2B (orange); whereas, the BLM model only contains subdomains 1A and 2A. (B) Electrostatic surface of the model with the same view as left. Negative potential is shown in red, positive potential in blue. The surface potential is negative over most of the surface except for the DNA-binding cleft. The docked ATP (green) is situated in the nucleotide-binding pocket between subdomains 1A and 2A. The merged DNA (yellow) with ribbon is located at the binding cleft with good complementarity. (C) Stereo diagram showing the structural model of the BLM helicase domain with the same view as above. (C-1) The seven conserved helicase motifs, I, Ia, II, III, IV, V and VI, are shown in blue, light blue, orange, magenta, red, white and green, respectively. The docked ATP is displayed in green. The nucleotide binding pocket is contributed by motifs I, II-IV and VI; whereas, the DNA binding cleft is formed by motifs Ia, III and V. (C-2) Secondary structure elements are indicated in red for α-helices and blue for β-strands. The residues of BS-causing mutations are displayed with sidechains in green and residue K695, corresponding to mutation K703A on mouse BLM, is also displayed.

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