O. Inanami et al., THE LEUKOCYTE NADPH OXIDASE SUBUNIT P47(PHOX) THE ROLE OF THE CYSTEINE RESIDUES, Archives of biochemistry and biophysics, 350(1), 1998, pp. 36-40
The leukocyte NADPH oxidase is a multi-subunit enzyme that catalyzes t
he reduction of oxygen to O-2(-) at the expense of a reduced pyridine
nucleotide. We have used site-directed mutagenesis to examine the func
tional role of the four cysteines in p47(PHOX), one of the subunits of
the oxidase. For these experiments, mutant proteins in which a single
cysteine was replaced with alanine were expressed in p47(PHOX)-defici
ent Epstein-Barr virus-transformed B lymphoblasts, and O-2(-) producti
on by these transfected cells was measured. The activity of the mutant
C98A was similar to that of wild type, but the maximum rate of O-2(-)
production by C196A was significantly larger than seen with wild type
, The other two mutants (i.e., C111A and C378A) differed from wild typ
e not only in maximum O-2(-) production, but also in the time required
for activation, which was considerably delayed with both of these mut
ants. The similarity in the time courses of oxidase activation with th
e C111A and C378A mutants, and the finding that C378A occurs in the se
quence CSE, raises the possibility that these cysteines may be involve
d in redox regulation of oxidase activity. (C) 1998 Academic Press.