INVESTIGADORES
DELGADO Monica Alejandra
congresos y reuniones científicas
Título:
The Plasmid pTUC200, encoding microcin J25, have unusual properties
Autor/es:
VALLEJOS, CECILIA; DELGADO, MONICA ALEJANDRA; VINCENT, PAULA A.; SALOMON, RAUL A.
Lugar:
Pinamar
Reunión:
Congreso; X Congreso PABMB; XXXXI Reunión Anual de SAIB and XX Annual meeting of SAN; 2005
Resumen:
MI-P50.
THE PLASMID pTUC200, ENCODING MICROCIN J25,
HAVE UNUSUAL PROPERTIES
Vallejos AC, Delgado MA, Vincent PA, Salomón RA.
Dep. de Bioquímica de la Nutrición. INSIBIO (UNT-CONICET)
Tucumán. E-mail: salomon@unt.edu.ar
Plasmid pTUC200 is a microcin J25 (MccJ25)-producing pBR322
derivative carrying a fragment from the wild-type MccJ25 plasmid,
pTUC100. This fragment includes a copy of the insertion sequence
IS1294 and the replicon of pTUC100. Plasmid pTUC200 has two
interesting properties. First, it suffers spontaneous deletions at a
low proportion. Second, it was stably maintained in a TolC- E. coli
strain. Note that other microcin-producing plasmids are lethal for
TolC- cells, since they cannot export the microcin produced.
Regarding the deletion phenomenon, although it occurred
spontaneously, its frequency was greatly increased in Tn5-carrying
pTUC200, or when the transposon was present in trans. The
nucleotide sequences of deletion junctions were determined for 4
deletants. All of them had lost a fragment containing the pTUC100
replicon. Deletions seem not to be the result of homologous
recombination. One of the deletions end points is invariable and
corresponds to the right end of IS1294. This suggests that the
deletions are a result of IS1294 intramolecular transposition. We
have as yet no explanation for the increase in deletion frequency in
the presence of Tn5. As for the stability of pTUC200 in TolCstrains,
genetic experiments showed that this is due to the prevalence
of the pTUC100 low-copy-number replicon over that of the vector
pBR322. This is unusual, since when two different replicons are
fused it is the high-copy-number one which prevails. The resulting
low expression of MccJ25 would maintain the intracellular antibiotic
concentration below a toxic level.