FEBS Letters

Upon dimerization by oxidation, Hsp33 functions as a molecular chaperone in prokaryotes. Previously published structures of both the inactive and active species are of doubtful relevance to the solution conformations since the inactive (reduced) crystal structure was dimeric, while the active (oxidized) species was crystallized with a truncation of its regulation domain. The interdomain contact site of the inactive monomer, identified in this work, is consistent with that previously observed in the reduced dimer crystal. In contrast, fluorescence quenching of the active dimer contradicted the results expected from the domain‐swapped fold observed in the truncated dimer crystal. The results of this study provide important new information concerning controversial issues in the activation process of Hsp33.

The primary structure of insulin from the Holocephalan fish, Hydrolagus colliei (the ratfish), has been established by automated Edman degradation as:

Selective adenosine receptor agonists and antagonists have marked effects on the outcome of cerebral ischemia, and adenosine receptors are expressed on astrocytes. In this study we examined the effects of various adenosine receptor agonists on the production of nitric oxide and the induction of iNOS in astrocytes activated by LPS/IFN‐γ and TNF‐α/IL‐1β and on the production of TNF‐α. Treatment of the cells with the A_2A receptor agonist CGS 21680 inhibited both NO production and iNOS expression induced by stimulation with either LPS/IFN‐γ or TNF‐α/IL‐1β, whereas the A₁ and A₃ receptor agonists, CPA and Cl‐IB‐MECA, respectively, did not have significant inhibitory effects. The inhibitory effect of the A_2A receptor agonist was antagonized by the specific A_2A receptor antagonist CSC. The A_2A agonist also exerted a small inhibitory effect on the production of TNF‐α. Similar inhibitory effects on the production of NO were obtained by cyclic AMP‐elevating reagents, such as forskolin and dibutyryl cyclic AMP. Our findings suggest that activation of the A_2A receptor inhibits NO production and iNOS expression likely via increased cAMP.

Analysis of a genomic fragment from the plant parasitic nematode Meloidogyne artiellia revealed the presence of a gene which, in bacteria, is involved in the formation of polyglutamate capsule. Searching of various databases, including the Caenorhabditis elegans genome sequence and the large EST datasets from a variety of parasitic nematodes, showed that no similar genes have been identified in other nematodes or in any other eukaryotic organisms. The M. artiellia gene has a typical eukaryotic structure and its mRNA is present in the intestine. The gene is expressed in all life cycle stages tested. These findings demonstrate horizontal gene transfer may be important in catalyzing the diversification of nematode lineages.

The 3D structure of the apo‐pseudoazurin (copper free pseudoazurin) from Alcaligenes faecalis strain S‐6 is determined and refined at pH 6.7 using X‐ray diffraction data to 1.85Åresolution. The final crystallographicR‐factor is 0.164. Comparing the structures of apo‐pseudoazurin and the native (Cu²⁺) protein, we observed limited differences ranging between 0.1–0.4Åat the vicinity of the copper site, at the loops connecting the secondary structural elements, at certain β‐strands and at the amino and car☐y termini of the protein.