A membrane-associated ATPase, PotA, is a component of the spermidine-preferential uptake system in prokaryotes that plays an important role in normal cell growth by regulating the cellular polyamine concentration. No three-dimensional structures of membrane-associated ATPases in polyamine-uptake systems have been determined to date. Here, the crystallization and preliminary X-ray diffraction analysis of PotA fromThermotoga maritimaare reported. Diffraction data were collected and processed to 2.7 Å resolution from both native and selenomethionine-labelled crystals. Preliminary crystallographic analysis revealed that the crystals belonged to the hexagonal space groupP3₁12 (orP3₂12), with unit-cell parametersa=b= 88.9,c= 221.2 Å, α = 90, β = 90, γ = 120°, indicating that a dimer was present in the asymmetric unit.