Table 2.

Metal content and catalytic properties of different forms of E. coli and N. meningitidis MsrBs

Enzyme	mol Zinc/mol enzyme	mol Iron/mol enzyme	kcat with Trx (sec−1)	kobs with DTT (sec−1)
Wild-type eMsrBa	0.80	0.08	0.18	0.010
Wild-type eMsrB apoform	0.02	0.02	2.10−2	1.7.10−3
C45D/C48S/C94S/C97S eMsrBb	0.02	0.02	<3.10−3	<1.10−3
Wild-type nmMsrB	0.01	0.01	0.20c	0.050
D45C/S48C/S94C/A97C nmMsrB	0.60	0.17	<3.10−3	0.045

For determination of the metal content of wild-type and mutant MsrBs, the values represent the average of three independent measurements (SD range 10%). The activities of wild-type and mutant enzymes were assayed with 150 mM D,L-Met-R,S-SO, 10 mM DTT, and 50–100 μM enzyme (SD range 10%) or with 20–150 mM D,L-Met-R,S-SO, 100–800 μM Trx, 1.28 μM Trx reductase, and 0.5–50 μM enzyme (SD range 10%) as described in Materials and Methods. For wild-type eMsrB, K_M values for L-Met-R,S-SO and Trx were 2.2 ± 0.6 mM and 140 ± 22 μM, respectively.

^a The kinetic parameters of the MsrBs with a bound metal were determined with a form having a zinc:iron ratio of 8:2.

^b Similar results were obtained with the C45D/C48S/C94S/C97A eMsrB.

^c From Olry et al. (2002).