INVESTIGADORES
CURATTI Leonardo
artículos
Título:
Evidence for nifU and nifS Participation in the Biosynthesis of
Autor/es:
DEHUA ZHAO; LEONARDO CURATTI; LUIS M. RUBIO
Revista:
JOURNAL OF BIOLOGICAL CHEMISTRY
Referencias:
Año: 2007 vol. 282 p. 37016 - 37025
ISSN:
0021-9258
Resumen:
The nifU and nifS genes encode the components of a
cellular
machinery dedicated to the assembly of [2Fe-2S] and
[4Fe-4S]
clusters required for growth under nitrogen-fixing
conditions.
The NifU and NifS proteins are involved in the production
of
active forms of the nitrogenase component proteins, NifH
and
NifDK. Although NifH contains a [4Fe-4S] cluster, the
NifDK
component carries two complex metalloclusters, the
iron-molybdenum
cofactor (FeMo-co) and the [8Fe-7S] P-cluster.
FeMo-co, located at the active site of NifDK, is composed
of 7
iron, 9 sulfur, 1 molybdenum, 1 homocitrate, and 1
unidentified
light atom. To investigate whether NifUS are required for
FeMo-co biosynthesis and to understand at what level(s)
they
might participate in this process, we analyzed the effect
of nifU
and nifS mutations on the formation of active NifB protein and
on the accumulation of NifB-co, an isolatable intermediate
of
the FeMo-co biosynthetic pathway synthesized by the
product
of the nifB gene. The nifU
and nifS
genes were required to accumulate
NifB-co in a nifN
mutant background. This result
clearly
demonstrates the participation of NifUS in NifB-co
synthesis
and suggests a specific role of NifUS as the major
provider of
[Fe-S] clusters that serve as metabolic substrates for the
biosynthesis
of FeMo-co. Surprisingly, although nifB expression was
attenuated in nifUS
mutants, the assembly of the [Fe-S]
clusters
of NifB was compensated by other non-nif machinery for the
assembly of [Fe-S] clusters, indicating that NifUS are not
essential
to synthesize active NifB.
