X-ray diffraction and high-resolution NMR spectroscopy of methyl 3-azido-2,3-dideoxy-alpha-D-lyxo-hexopyranoside

The single-crystal X-ray diffraction and high-resolution 1H and 13C NMR spectral data for the title compound are reported. The influence of the ring oxygen atom on the J(1,2e) and J(4,5) coupling constants for 2-deoxy-D-lyxo- and -D-xylo-hexopyranosides is discussed.     

The use of tri-O-acetyl-D-glucal and -D-galactal in the synthesis of 3-acetamido-2,3-dideoxyhexopyranoses and -hexopyranosides

Addition of hydrazoic acid to alpha,beta-unsaturated aldehydes derived from tri-O-acetyl-D-glucal and -D-galactal gave 3-azido-2,3-dideoxyhexopyranoses. These were converted into 1,4,6-tri-O-acetyl-3-azido-2,3-dideoxyhexopyranoses as well as methyl and ethyl glycosides. Hydrogenation of the proamine group in 3-azido-2,3-dideoxy derivatives provided different 3-amino and 3-acetamido sugars. The configuration and conformation of all products were established on the basis of the 1H and 13 C NMR, IR and polarimetric data.     

A bichaperone (Hsp70-Hsp78) system restores mitochondrial DNA synthesis following thermal inactivation of Mip1p polymerase

Mitochondrial DNA synthesis is a thermosensitive process in the yeast Saccharomyces cerevisiae. We found that restoration of mtDNA synthesis following heat treatment of cells is dependent on reactivation of the mtDNA polymerase Mip1p through the action of a mitochondrial bichaperone system consisting of the Hsp70 system and the Hsp78 oligomeric protein. mtDNA synthesis was inefficiently restored after heat shock in yeast lacking either functional component of the bichaperone system. Furthermore, the activity of purified Mip1p was also thermosensitive; however, the purified components of the mitochondrial bichaperone system (Ssc1p, Mdj1p, Mge1p, and Hsp78p) were able to protect its activity under moderate heat shock conditions as well as to reactivate thermally inactivated Mip1p. Interestingly, the reactivation of endogenous Mip1p contributed more significantly to the restoration of mtDNA synthesis than did import of newly synthesized Mip1p from the cytosol. These observations suggest an important link between function of mitochondrial chaperones and the propagation of mitochondrial genomes under ever-changing environmental conditions.     

Hsp70 chaperone machine remodels protein aggregates at the initial step of Hsp70-Hsp100-dependent disaggregation

Exposure to temperatures over a certain limit leads to massive protein aggregation in the cell. Disaggregation of such aggregates is largely dependent on the Hsp100 and Hsp70 chaperones. The exact role of the Hsp70 chaperone machine (composed of DnaK, DnaJ, and GrpE) in the Hsp100-dependent process remains unknown. In this study we focused on the Hsp70 role at the initial step of the disaggregation process. Two different aggregated model substrates, green fluorescent protein (GFP) and firefly luciferase, were incubated with the Hsp70 machine resulting in efficient fragmentation of large aggregates into smaller ones. Our data suggest that the observed fragmentation is achieved first by extraction of polypeptides from aggregates in Hsp70 chaperone machine-dependent manner and not by direct fragmentation of large aggregates. In the absence of Hsp100 (ClpB) these "extracted" polypeptides were not able to fold properly and promptly reassociated into new aggregates. The extracted GFP molecules were efficiently recognized and sequestered by a molecular trap, the mutant GroEL D87K, which binds stably to unfolded but not to native polypeptides. The binding of extracted GFP molecules to the GroEL trap prevented their reaggregation. We propose that the Hsp70 machine disentangles polypeptides from protein aggregates prior to Hsp100 action.     

Synthesis and geometry of methyl (methyl 4-O-acetyl-3-azido-2,3-dideoxy-alpha/beta-D-arabino- and -alpha/beta-D-ribo-hexopyranosid)uronates

The synthesis of methyl (methyl 4-O-acetyl-3-azido-2,3-dideoxy-alpha/beta-D-arabino- and -alpha/beta-D-ribo-hexopyranosid)uronates is presented. High resolution (1)H and (13)C NMR spectral data for all diastereoisomers and single-crystal X-ray diffraction analysis for methyl (methyl 3-azido-2,3-dideoxy-beta-D-arabino-hexopyranosid)uronate are reported. The planarity of the 4-OAc and 5-COOMe groups as well as the orientations of the aglycone and azide groups in the crystal lattice is discussed. The influence of the 5-COOMe group on the pyranose ring conformation is considered.     

Importance of two ATP-binding sites for oligomerization, ATPase activity and chaperone function of mitochondrial Hsp78 protein.

The yeast mitochondrial chaperone Hsp78, a homologue of yeast cytosolic Hsp104 and bacterial ClpB, is required for maintenance of mitochondrial functions under heat stress. Here, Hsp78 was purified to homogeneity and shown to form a homo-hexameric complex, with an apparent molecular mass of approximately 440 kDa, in an ATP-dependent manner. Analysis of its ATPase activity reveals that the observed positive cooperativity effect depends both on Hsp78 and ATP concentration. Site-directed mutagenesis of the two putative Hsp78 nucleotide-binding domains suggest that the first nucleotide-binding domain is responsible for ATP hydrolysis and the second one for protein oligomerization. Studies on the chaperone activity of Hsp78 show that its cooperation with the mitochondrial Hsp70 system, consisting of Ssc1p, Mdj1p and Mge1p, is needed for the efficient reactivation of substrate proteins. These studies also suggest that the oligomerization but not the Hsp78 ATPase activity is essential for its chaperone activity.     

Effects of drugs used in high-risk pregnancy on child development

The study involved 60 children delivered by the mothers of risk group who were given gestagens and beta-adrenomimetics during pregnancy. Physical, motoric development and morbidity in this group of children with particular relation to respiratory diseases were subject to our study. Thirty eight children delivered by healthy mothers were used as a control group. It was found that there was no developmental abnormalities in children from pregnancies maintained with gestagens and beta-adrenomimetics. Morbidity rate was the same in the tested and control groups.