There are four crystallographically independent AaNusG molecules (A through D) in the crystal lattice of the P2₁ structure. Mol A (blue) and B (yellow) form a domain-swapped dimer, six of which are shown. Mol C (red) and D (green) form the repeating unit of a polymer; a polymer with six repeating units is shown. F232 (ball) is highlighted [Knowlton JR, Bubunenko M, Andrykovitch M, Guo W, Routzahn KM, Waugh DS, Court DL, and Ji X. Biochemistry (Accelerated Publications) 2003; 42:2275-2281. Abstract].