The structure of DinB from Geobacillus stearothermophilus: a representative of a unique four-helix-bundle superfamily

Acta Cryst. (2010). F66, 219–224 (doi.org/10.1107/S1744309109053913)

Ribbon diagram of a monomer of DinB colored with a spectrum from the N-terminus (blue) to the C-terminus (red). The Ni²⁺-coordinating histidine triad is shown as sticks and the Ni²⁺ ion is shown as a green sphere.

Geobacillus stearothermophilus DinB (GsDinB) is a dimer encoded by a DNA damage-induced gene under the control of the SOS-like repair systems. Monomers consist of an unusual up–down–down–up four-helix bundle with the α₁/α₂ loop crossing over the top of the bundle and the α₃/α₄ loop wrapping under the bundle. GsDinB contains a metal-binding histidine triad motif. Structural similarity searches reveal a small yet diverse clan of Pfam families containing this fold. At least four different quaternary structures, including three dimerization architectures, have been observed.