Proteum software suite

X-ray data sets were collected in house using a Bruker AXS Platinum 135 CCD detector controlled with the Proteum software suite (Bruker AXS Inc.) The X-ray source was Cu Kα radiation from a Rigaku RU200 X-ray generator equipped with Montel optics and operated at 50 kV and 90 mA. The X-ray data sets were processed with SAINT and scaled with SADABS (Bruker AXS Inc.). Relevant X-ray data collection statistics are listed in Table 1.
The structure of KdnA was determined via molecular replacement using the software package PHASER,^{11 (link)} with the coordinates of QdtB serving as the search model.^{12 (link)} 4-fold averaging and solvent flattening yielded an electron density map that allowed for essentially a complete tracing of the KdnA polypeptide chain. The model was subjected to alternate cycles of refinement with REFMAC^{13 (link)} and manual model building with COOT.^{14 (link),15 (link)} KdnB was also solved using PHASER with the search model being that of PDB entry 3RF7. The KdnB model was refined in a similar manner as that for KdnA. Model refinement statistics are listed in Table 2.

The data were collected using a Bruker AXS Platinum 135 CCD detector controlled with the PROTEUM software suite (Bruker AXS Inc., Madison, WI). The X-ray source was CuK radiation (1.54178 Å) from a Rigaku RU200 X-ray generator equipped with Montel optics, operated at 50 kV and 90 mA. The X-ray data were processed with SAINT version 7.06A (Bruker AXS Inc.) and internally scaled with SADABS version 2005/1 (Bruker AXS Inc.). The sample was mounted on a glass fiber using vacuum grease and cooled to 100 K. The intensity data were measured as series of phi and omega oscillation frames each of 1° for 5-20 sec/frame. The detector was operated in 512 × 512 mode and was positioned 4.5 cm from the sample. Cell parameters were determined from a non-linear least squares fit in the range of 4.0The space group was determined by systematic absences and statistical tests and verified by subsequent refinement. The structure was solved by direct methods²⁸ and refined by the full-matrix least-squares methods on F^{2 (link)}. The hydrogen atom positions were determined from difference peaks and ultimately refined by a riding model with idealized geometry. Non-hydrogen atoms were refined with anisotropic displacement parameters. The absolute structure was determined by refinement of the Flack parameter.²⁹ Crystallographic data for the structures reported in this paper have been deposited at the Cambridge Crystallographic Data Center with the deposition numbers: CCDC 1402441 (3) and CCDC 1402442 (5).