ScMreB5 is stabilized by KCl and nucleotides. (A) X-ray fluorescence scan for ScMreB5-AMP-PNP crystals. (B) Coordination sphere of potassium in ScMreB5-ADP (top) and ScMreB5-AMP-PNP (bottom). (C) Melting curve for ScMreB5 showing T_m for varying concentrations (orange, 100 mM; purple, 200 mM; and green, 300 mM) of NaCl (dotted line) and KCl (solid line). (D) Melting curve for ScMreB5 showing T_m of ScMreB5 without any nucleotide (red), 1 mM ADP (blue), and 1 mM ATP (green). (E) HPLC run in DNAPac PA 200 column for 20 mmol of denatured ScMreB5^WT supernatant fraction shows absorbance at 255 nm (milli absorbance unit [mAU]) of bound ADP peak compared to the standard ADP run. ADP and ATP standards are 40 mmol each. (F) Asp12 and Asn17 of ScMreB5 at the potassium-binding site are compared with the corresponding residue present in monomeric (PDB accession no. 4CZM) and double-protofilament CcMreB (PDB accession no. 4CZJ) by superposing IIA subdomain of CcMreBs onto IIA subdomain of ScMreB5–AMP-PNP structure (single protofilament conformation). The presence of a water molecule in the CcMreB at the potassium-equivalent position can be observed. The residues of ScMreB5 are colored domain-wise; those of CcMreB are light blue. The water molecules for ScMreB5 are red, and for CcMreBs, yellow.