Table 2: Metal-to-protein ratios and molecular masses of the recombinant Zn(II)-MT, complexes obtained from the pGEX expression system with no metal supplementation to the culture, except in the Zn-MtnB used as a control (see Section 2). All the measurements have been performed at least twice, from independently obtained samples.

MT proteinZn/MT Zn/MT Zn-MT species
(ICP-AES)(acidic ICP-AES)(ESI-MS)

mMT16.957.40Zn7-mMT16605.56605.96

Crs54.204.61Zn4-Crs57715.57718.92
Zn3-Crs5 Zn5-Crs57654.5 7780.57655.53 7782.31
Zn2-Crs5 Zn6-Crs57590.4 7844.57592.13 7845.70
Zn1-Crs5 Zn7-Crs57525.0 7907.57528.75 7909.09

MtnB2.042.40apo-MtnB4667.24669.34
Zn1-MtnB4733.84732.73
Zn3-MtnB4857.04859.51
Zn2-MtnB4795.04796.12
Zn4-MtnB4920.84922.9

MtnA1.701.94apo-MtnA Zn1-MtnA3996.4 4059.43997.49 4060.88
Zn2-MtnA4121.24124.27
Zn3-MtnA4186.44187.66

Zn-MtnB 3.955.10Zn4-MtnB4922.04922.90
Zn3-MtnB4850.24859.51

ICP-AES inductively coupled plasma atomic emission spectroscopy, ESI-MS electrospray ionization mass spectrometry.
In all experiments Cd and Cu contents were also measured but their amount was always under detection limits.
Species proposed according to the mass difference between holo-protein and apo-protein. Species in bold are the major components of the preparation.
Experimental molecular masses. Measurements were always performed in duplicate. All corresponding standard deviations were always less than 1%.
Theoretical molecular mass of the corresponding species.
Control experiment: MtnB synthesized in Zn(II)-supplemented medium.