Bariloche protein symposium argentine society for biochemistry and molecular biology

60
BIOCELL, 27 (Suppl. I), 2003
MI-P3.
INTERACTION BETWEEN THE Salmonella
PATHOGENICITY ISLAND 1  AND THE PhoP/PhoQ
SYSTEM
Aguirre, Andrés; Cabeza, M. Laura; García Véscovi, Eleonora;
and Soncini, Fernando C.
Instituto de Biología Molecular y Celular de Rosario (CONICET),
and Facultad de Ciencias Bioquímicas y Farmacéuticas (UNR),
Rosario, Argentina. E-mail: [e-mail]
Salmonella infections are initiated when organisms penetrate the
epithelial cells within the small intestine. Proteins encoded by a
cluster of genes on the chromosome known as “Salmonella
Pathogenicity Island 1” (SPI-1) play a critical role in the invasion
process.  The expression of most of these genes requires HilA, a
transcription factor encoded on SPI-1.  Expression of hilA is
complex, and it has been demonstrated to be repressed in a
Salmonella strain harboring a phoQ mutant allele, pho24.  This
mutant  codes for a sensor protein that is more active at Mg
2+
-
repressing conditions than the wild-type.  However, neither the
link that connects PhoP/PhoQ with hilA regulation nor its Mg
2+
dependence has yet been elucidated.
Using microarrays, we have detected a PhoP activated gene
encoded within SPI1.  By creating a lacZ transcriptional fusion to
this gene, we confirmed its dependence on PhoP/PhoQ, and Mg
2+
concentration. Interestingly, a deletion in this locus increased hilA
expression.  We propose this gene to be the connection between
the Salmonella Pathogenicity Island 1 and the PhoP/PhoQ system.
MI-P4.
BEHAVIOR OF RHODOCOCUS OPACUS DURING
DESICCATION IN THE PRESENCE OF HEXADECANE
VAPORS
Alvarez, Héctor M.; Silva, Roxana A.; Zamit, Ana L.; Cesari, Ana
C.; Alvarez, Adrián F. and Ramírez Verónica.
Depto de Bioquímica, Facultad de Ciencias Naturales,
Universidad Nacional de la Patagonia, Comodoro Rivadavia,
Argentina. E-mail: [e-mail]
Desiccation plays a determinative role in the survival of
microorganisms in the environment, principally in desert regions
such as in the semiarid Patagonia. The aim of this study was to
investigate the behavior of the soil isolate Rhodococcus  opacus
PD630 subjected to desiccation during exposure of hexadecane
vapors. Similar situation is found in natural arid environments
contaminated with hydrocarbons during non-rainy periods.
Exposure of desiccated cells to hexadecane vapors produced the
following effects: 1) hexadecane likely exerted a toxic action at
the cellular envelope level resulting in cell deformation and a
decrease of survival; 2) removal of an extracellular polymer
accumulated at colony surfaces during desiccation; 3) production
of microcolonies principally in the inner sector of colonies; 4)
mobilization of storage lipids (triacylglycerols) presumably for
producing the energy necessary for the re-adaptation of cellular
physiology; 5) turnover of fatty acids and mycolic acids. Results
of this study suggested that R. opacus colonies contain cells with
different physiological status, some of them being not able to
survive under these conditions, whereas others respond actively
to the presence of hexadecane vapors during desiccation.
MI-P5.
REDOX-DEPENDANT STRUCTURAL MODIFICATIONS
OF tHE SCHISTOSOMA MANSONI GLUTATHIONE S-
TRANSFERASE OMEGA
Amirante, Alejandro; Girardini, Javier Enrique; Serra, Esteban.
IBR-CONICET. Facultad de Cs. Bioq. y Farm. de Rosario. UNR.
E-mail: [e-mail]
The gluthatione S-transferases (GSTs) play a key role in phase II
of enzymic detoxification of a wide variety of both endogenous
and exogenous electrophilic compounds. GSTs are considered the
most prominent detoxifying enzymes in helminths. We have cloned
an Omega class GST gene from Schistosoma mansoni (SmGSTO).
The recombinant enzyme shown glutathione-dependent
dehydroascorbate reductase, and thiol transferase activities; but
low activity towards the classical substrate, CDNB. Spectroscopic
experiments showed a structural modification of the enzyme related
to its redox state. Reduced form of the enzyme is monomeric. In
contrast, in presence of GSSG the enzyme partially dimmerized.
The dimmer can be monomerized by DTT or GSH, suggesting the
existence of a disulfide bond. The enzyme was able to bind to S-
hexyl glutathione agarose, only in its reduced state. Western Blot
experiments performed with total protein extracts of adult
parasites, cultured under normal or stress conditions (cumene
hydroperoxide and hydrogen peroxide), shown that SmGSTO is
in its monomer oxidized state. We also observed a greater
expression of SmGSTO in male than in female.
Immunohistochemistry assays showed that tissues with mayor
expression are, intestinal parenchyma, and tegument (including
spines and tubercles) exposed to the media. We could not detect
SmGSTO neither in ovary nor in testis.
MI-P2.
EXPRESSED SEQUENCE TAGS FROM Trypanosoma cruzi
TRYPOMASTIGOTE AND AMASTIGOTE-LIKE FULL-
LENGTH cDNA LIBRARIES
Fernán Agüero
1
, Karim Ben Abdellah
2
, Daniel O. Sánchez
1 
and
Antonio González
2
.
1
Instituto de Investigaciones Biotecnológicas, Universidad
Nacional de General San Martín - CONICET, Buenos Aires,
Argentina.
  2
Instituto de Parasitologia y Biomedicina, Granada,
España.  E-mail: [e-mail]
We have generated 2,796 expressed sequence tags (ESTs) from
two cDNA libraries of Trypanosoma cruzi CL-Brener. The libraries
were constructed from trypomastigote and amastigote-like forms,
using a spliced leader primer (miniexon) to synthesize the cDNA
second strand, thus selecting for full-length cDNAs. Since the
libraries were not normalized nor pre-screened, we compared the
representation of transcripts between the two and identify a subset
of transcripts that show apparent differential representation. A non-
redundant set of 1,626 reconstructed transcripts was generated by
sequence clustering. This dataset was used to perform similarity
searches against protein and nucleotide databases. 432 ESTs could
be assigned a putative identity based on these searches. These are
the first ESTs reported for the life cycle stages of T. cruzi that
occur in the vertebrate host.  481 of these ESTs (29.6%) are novel
sequences, not represented in the ESTs obtained from the
epimastigote normalized library from which the great majority of
the T. cruzi ESTs were derived.

---