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. Author manuscript; available in PMC: 2010 Mar 10.
Published in final edited form as: Biochemistry. 2009 Mar 10;48(9):1945–1953. doi: 10.1021/bi802254x

Table 3.

Rate constants kobs (min−1) of iron release for iron-containing N-lobe and N-lobe mutants monitored by the increase in fluorescence (Figure 3) or by the decrease in absorbance at 280 nm (kinetic traces not shown). Measurements were made in 100 mM MES, pH 5.6 and 4 mM EDTA,

Protein Fluorescence kobsN (min−1) I1/I2/I3 (%)b Absorbance kobsN (min−1) I1/I2 (%)c
N-lobe (wild-type)a 8.9 ± 0.8
1.3 ± 0.3		 64
36		 8.0 ± 0.9 100
G65R (HCO3−)a 322.7 ± 23
13.6 ± 3		 95
5		 411.6 ± 30 100
G65R (HEPES)a 370.4 ± 10
58.9 ± 3
3.7 ± 0.1		 83
9
8		 427.2 ± 26
36.7 ± 3		 83
17
G65R (Fe3+(NTA)2)a 318.0 ± 2
13.7 ± 0.6		 92
8		 305.4 ± 31 100
G65R/K206E 1.0 ± 0.01 100
K206E Too slow to measure accurately
a

Kinetic data was fit to a sum of exponentials (see Material and Methods).

b

I1 I2 and I3 refer to the % change in fluorescent intensity corresponding to kobsN1 kobsN2, and kobsN3, respectively.

c

I1 and I2 refer to the % change in absorbance intensity corresponding to kobsN1 and kobsN2, respectively.