Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 23

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
groES and groEL genes encode two co-operating proteins GroES and GroEL, belonging to a class of chaperone proteins highly conserved during evolution. The GroE chaperones are indispensable for the growth of bacteriophage λ in Escherichia coli cells. In order to clone the groEL and groES genes of the marine bacterium Vibrio harveyi, we constructed the V. harveyi genomic library in the λEMBL1 vector, and selected clones which were able to complement mutations in both groE genes of E. coli for bacteriophage λ growth. Using Southern hybridization, in one of these clones we identified a DNA fragment homologous to the E. coli groE region. Analysis of the nucleotide sequence of this fragment showed that the cloned region contained a sequence in 71.7% homologous to the 3' end of the groEL gene of E. coli. This confirmed that the λ clone indeed carries the groE region of V. harveyi. The positive result of our strategy of cloning with the use of the genomic library in λ vector suggests that the same method might be useful in the isolation of the groE homologues from other bacteria. The V. harveyi cloned groE genes did not suppress thermosensitivity of the E. coli groE mutants.
 Rheumatoid arthritis (RA) is a chronic, systemic inflammatory disease which affects approximately 1 % of the population worldwide. Recent research on the role of heat shock proteins (Hsps) in RA development indicates that they may have pro- or anti-inflammatory effect, most probably via modulating cytokine secretion. We investigated type Th1 (INFγ, TNFα, IL-2) and type Th2 (IL-10, IL-6, IL-4) cytokine levels in sera of RA patients and healthy controls, using flow cytometric bead array assay, and searched for correlations between the cytokine levels and serum antibodies against bacterial (DnaJ) and human (Hdj1, Hdj2 and Hdj3) Hsp40 proteins, as well as clinical and laboratory parameters. The levels of all cytokines studied were significantly increased in RA patients; the highest increase relative to healthy controls (7-fold) was observed for IL-6 and its levels correlated positively with the antibodies directed to DnaJ and to the C-terminal domain of Hdj2, and with diagnostic parameters (DAS 28, Steinbrocker RTG criteria, ARA/7, ESR, TEN, SW and GH). INFγ levels correlated negatively with DAS 28, ESR, TEN and SW. No correlations were found for TNFα, IL-2 or IL-4. Our results support the hypothesis of Hsp40 involvement in RA as well as indicate that IL-6 serum level is a good marker of the RA activity.
Escherichia coli small heat shock proteins, IbpA/B, function as molecular chape- rones and protect misfolded proteins against irreversible aggregation. IbpA/B are in­duced during overproduction of recombinant proteins and bind to inclusion bodies in E. coli cells. We investigated the effect of AibpA/B mutation on formation of inclu­sion bodies and biological activity of enzymes sequestered in the aggregates in E. coli cells. Using three different recombinant proteins: Cro-ß-galactosidase, ß-lactamase and rat rHtrA1 we demonstrated that deletion of the ibpA/B operon did not affect the level of produced inclusion bodies. However, in aggregates containing IbpA/B a higher enzymatic activity was detected than in the IbpA/B-deficient inclusion bodies. These results confirm that IbpA/B protect misfolded proteins from inactivation in vivo.
Hsp70 (DnaK) is a highly conserved molecular chaperone present in bacteria, eukaryotes, and some archaea. In a previous work we demonstrated that DnaK from the archaeon Methanosarcina mazei (DnaKMm) and the DnaK from the bacterium Escherichia coli (DnaKEc) were functionally similar when assayed in vitro but DnaKMm failed to substitute for DnaKEc in vivo. Searching for the molecular basis of the observed DnaK species specificity we compared substrate binding by DnaKMm and DnaKEc. DnaKMm showed a lower affinity for the model peptide (a-CALLQSRLLS) compared to DnaKEc. Furthermore, it was unable to negatively regulate the E. coli σ32 transcription factor level under heat shock conditions and poorly bound purified σ32, which is a native substrate of DnaKEc. These observations taken together indicate differences in substrate specificity of archaeal and bacterial DnaKs. Structural modeling of DnaKMm showed some structural differences in the substrate-binding domains of DnaKMm and DnaKEc, which may be responsible, at least partially, for the differences in peptide binding. Size-exclusion chromatography and native gel electrophoresis revealed that DnaKMm was found preferably in high molecular mass oligomeric forms, contrary to DnaKEc. Oligomers of DnaKMm could be dissociated in the presence of ATP and a substrate (peptide) but not ADP, which may suggest that monomer is the active form of DnaKMm.
Hsp70s are chaperone proteins that are conserved in evolution and present in all prokaryotic and eukaryotic organisms. In the archaea, which form a distinct kingdom, the Hsp70 chaperones have been found in some species only, including Methanosarcina mazei. Both the bacterial and archaeal Hsp70(DnaK) chaperones cooperate with a GrpE co-chaperone which stimulates the ATPase activity of the DnaK protein. It is currently believed that the archaeal Hsp70 system was obtained by the lateral transfer of chaperone genes from bacteria. Our previous finding that the DnaK and GrpE proteins of M. mazei can functionally cooperate with the Escherichia coli GrpE and DnaK supported this hypothesis. However, the cooperation was surprising, considering the very low identity of the GrpE proteins (26%) and the relatively low identity of the DnaK proteins (56%). The aim of this work was to investigate the molecular basis of the observed interspecies chaperone interaction. Infrared resolution-enhanced spectra of the M. mazei and E. coli DnaK proteins were almost identical, indicating high similarity of their secondary structures, however, some small differences in band position and in the intensity of amide I' band components were observed and discussed. Profiles of thermal denaturation of both proteins were similar, although they indicated a higher thermostability of the M. mazei DnaK compared to the E. coli DnaK. Electrophoresis under non-denaturing conditions demonstrated that purified DnaK and GrpE of E. coli and M. mazei formed mixed complexes. Protein modeling revealed high similarity of the 3-dimensional structures of the archaeal and bacterial DnaK and GrpE proteins.
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.