CEFOBI   05405
CENTRO DE ESTUDIOS FOTOSINTETICOS Y BIOQUIMICOS
Unidad Ejecutora - UE
artículos
Título:
Identification of domains involved in the allosteric regulation of cytosolic Arabidopsis thaliana NADP-malic enzymes
Autor/es:
GERRARD WHEELER, M. C.; ARIAS, C. L.; MAURINO, V. G.; ANDREO, C. S.; DRINCOVICH, M. F.
Revista:
FEBS JOURNAL
Editorial:
WILEY-BLACKWELL PUBLISHING, INC
Referencias:
Año: 2009 p. 5665 - 5677
ISSN:
1742-464X
Resumen:
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The Arabidopsis thaliana genome contains four genes encoding NADP-malic
enzymes (NADP-ME1 to -4). Two isoenzymes, NADP-ME2 and -3, which are shown to
be located in the cytosol, share a remarkably high degree of identity (90%).
However, they display different expression patterns and show distinct kinetic
properties, especially with regard to their regulation by effectors, both in
the forward -malate oxidative decarboxylation- and the reverse -pyruvate
reductive carboxylation- reactions. In order to identify domains in the primary
structure that could be responsible for the regulatory differences, four
chimeras between these isoenzymes were constructed and analysed. All chimeric
versions exhibited the same native structures as the parental proteins.
Analysis of the chimeras constructed indicated that the region from amino acid
residue 303 to the C-terminal end of NADP-ME2 is critical for fumarate
activation. On the other hand, the region flanked by the amino acid residues
303 and 500 of NADP-ME3 is involved in the pH dependent-inhibition by high
malate concentration. Furthermore, the N-terminal region of NADP-ME2 is
necessary for the activation by succinate of the reverse reaction. Overall, the
results show that NADP-ME2 and -3 are able to distinguish and interact
differentially with similar C4 acids due to minimal structural differences.
Therefore, although the active sites of NADP-ME2 and -3 are highly conserved,
both isoenzymes acquired different allosteric sites, leading to the creation of
proteins with unique regulatory mechanisms, probably best suited to the
specific organ and developmental pattern of expression of each isoenzyme.