Table 1. Crystallization conditions.

Crystals of the same crystal form but obtained from different conditions were generally of similar quality. The ‘best’ data are represented in Table 2 ▶.

	Protein solution	Reservoir solution	Temperature (K)	Cryoprotection
HigBA2 form I	10 mg ml−1 in 20 mM Tris pH 8, 200 mM NaCl	100 mM bicine/Tris pH 8.5, 12.5%(w/v) PEG 1000, 12.5%(w/v) PEG 3350, 12.5%(w/w) MPD, 30 mM NaF, 30 mM NaBr, 30 mM NaI	293	None
	10 mg ml−1 in 20 mM Tris pH 8, 200 mM NaCl	20%(v/v) ethanol, 100 mM Tris–HCl pH 8.5	293	35% glycerol
	10 mg ml−1 in 20 mM Tris pH 8, 200 mM NaCl	2.0 M ammonium phosphate monobasic, 100 mM Tris–HCl pH 8.5	293	25% glycerol
	15 mg ml−1 in 50 mM Tris pH 7.5, 150 mM NaCl	50 mM Tris–HCl pH 8.5, 200 mM magnesium acetate, 22–28%(w/v) PEG 8000	293	Increase PEG to 35%
HigBA2 form II	10 mg ml−1 in 20 mM Tris pH 8, 200 mM NaCl	200 mM ammonium sulfate, 100 mM sodium cacodylate trihydrate pH 6.5, 30%(w/v) PEG 8000	293	Increase PEG to 40%
	10 mg ml−1 in 20 mM Tris pH 8, 200 mM NaCl	2.0 M ammonium sulfate, 2%(w/v) PEG 400, 100 mM HEPES pH 7.5	293	20% glycerol
HigA2 C-terminal domain†	5 mg ml−1 in 20 mM Tris pH 8, 200 mM NaCl	100 mM Tris–HCl pH 8.5, 200 mM calcium chloride, 20%(w/v) PEG 4000	293	Increase PEG to 36.6%
	5 mg ml−1 in 20 mM Tris pH 8, 200 mM NaCl	20%(w/v) PEG 3350, 200 mM potassium thiocyanate, 100 mM bis-tris propane	277	10% glycerol
	5 mg ml−1 in 20 mM Tris pH 8, 200 mM NaCl	30%(w/v) PEG 4000, 100 mM Tris pH 8.5, 200 mM sodium acetate trihydrate	293	Increase PEG to 40%

^†The protein concentration corresponds to the full-length protein.