IBR   13079
INSTITUTO DE BIOLOGIA MOLECULAR Y CELULAR DE ROSARIO
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
CcpA represses the divergent cit operon of Enterococcus faecalis through multiple cre sites
Autor/es:
BLANCATO, VICTOR; SUÁREZ C.; PINCET, S; DEUTSCHER, J; MAGNI, CHRISTIAN
Lugar:
Puerto Madryn
Reunión:
Congreso; XLVI Reunión Anual de SAIB; 2010
Institución organizadora:
Sociedad Argentina de Investigación en Bioquímica y Bilogía Molecular
Resumen:
In E. faecalis the genes encoding
the enzymes involved in citrate metabolism are organized in two
divergent operons, citHO and oadHDB-citCDEFX-oadA-citMG (citCL). Both operons are specifically activated by addition of citrate to culture
medium. We observed that the citHO and citCL promoters are
repressed in the presence of sugars transported by the PTS, strongly
suggesting a Carbon Catabolic Repression (CCR). Moreover, our results showed
that repression was relieved in a ccpA-deficient E. faecalis strain
indicating that the pleiotropic transcriptional factor CcpA was involved in the
regulation. Sequence analysis of the proximal intergenic region of the cit operons revealed the presence of
three putative catabolite responsive elements (cre). In this work, we analyzed the role of CcpA
and cre sites in the regulation of citrate metabolism. By gel mobility
shift assays (EMSA) we confirmed that E. faecalis CcpA is capable of
binding to each cre site. Furthermore, we analyzed the effect of its cofactor,
HPr. The results indicated that unphosphorylated HPr showed a minor increase in
CcpA affinity for the cre sites, whereas serine-phosphorylated HPr (P-Ser-HPr) produced a significant
increase in affinity. Thus,
in E. faecalis the binding of the P-Ser-HPr-CcpA complex to the cre
sites repressed the
expression of the activator CitO and also inhibited the expression of the
catabolic genes.