Table 1. Metal content of as-isolated ZmGLX1 measured by atomic absorption spectroscopy.

Metal content is defined as the ratio of the metal:protein molar concentrations. The buffer is 50mM TrisHCl, 0.2M NaCl pH 7.2. ND, not detected.

	Metal content
Metal	Trace-metals ZmGLX1	Ni-only ZmGLX1	His6-less ZmGLX1	His6-less E114Q ZmGLX1
Ca	0.4 0.1	ND	ND	ND
Zn	0.10 0.05	ND	ND	ND
Co	0.08 0.03	ND	ND	ND
Ni	0.07 0.02	0.80 0.02	0.80 0.20	0.30 0.10