The ribosome-associated inhibitor A reduces translation errors

Recently we have reported about a novel stress response protein (pY or RaiA) associated with Escherichia coli ribosomes that inhibits translation at the aminoacyl-tRNA binding stage. Here we show that leucine misincorporation during in vitro poly(U) translation is inhibited by this protein much stronger than the incorporation of phenylalanine. The miscoding counteraction by RaiA is especially strong at the concentrations of magnesium ions close to those observed in vivo and diminishes at higher magnesium concentrations. The results obtained suggest that the anti-miscoding activity of RaiA could be the main function of the protein, rather than the inhibition of translation. The role of the protein in adaptation of cells to environmental stress is discussed.     

Synthesis and maturation of green fluorescent protein in a cell-free translation system

Summary A cell-free translation system producing mature green fluorescent protein (GFP) can be a useful tool for studying the mechanism and kinetics of GFP chromophore formation, as well as for fast protein engineering. We report here that the mature GFP can be formed in the cell-free translation system from E.coli. The synthesis of GFP in the cell-free system reaches a plateau in 30 to 40 min whereas its maturation is completed in 4 h from the beginning of translation. The delay between the GFP synthesis and the chromophore formation in the cell-free system provides the possibility to isolate and to analyse maturation intermediates for elucidation of the modification pathway.     

CHANGES IN CHEMICAL, SENSORY AND RHEOLOGICAL CHARACTERISTICS OF MANCHEGO CHEESES DURING RIPENING

Manchego cheese is a high-fat pressed ewe's-milk cheese made in Castilla-La Mancha (Spain) and produced by enzymatic coagulation. The minimum ripening time before marketing required by the Regulatory Board of the Manchego Cheese Appellation of Origin is 60 days.
This paper describes the physicochemical, proteolysis, sensory and texture characteristics of Manchego cheese, and the degree of homogeneity of cheeses made under the Manchego Appellation of Origin. The data gathered in this study indicate that sensory and instrumental analysis are useful tools for detecting changes in Manchego cheese during ripening. These changes were first detected by the instrumental analysis (2 months). The panelists detected differences after 4 months' ripening in all the factories. With physicochemical analysis, on the other hand, longer ripening times (6–8 months) are required before such changes become appreciated.     

Karyological studies in Sonchus section Muritimi (Asteraceae) from the Iberian Peninsula

MEJÍAS, J. A. & VALDÉS, B., 1988. Karyologiepl studies in Sonchus section Madtimi (Asteraceae) from the Iberian Peninmula. Karyological data support the distinction of S. aquatilis Pourret and S. maritimus L. at the specific level. Karyological data and hybridization experiments support the idea that S. × novocaslcllanus Cirujano has been produced by the hybridization of S. crassifolius Pourret ex Willd. and S. maritimus L.     

Template-free ribosomal synthesis of polypeptides from aminoacyl-tRNAs

In the present paper it has been demonstrated that Escherichia coli ribosomes in the absence of messenger polynucleotides are capable of synthesizing some polypeptides from aminoacyl-tRNAs as substrates. EF-Tu induced binding of aminoacyl-tRNA, ribosomal peptidyl transferase and EF-G-promoted translocation are strictly required for this template-free elongation.Typical ribosomal inhibitors such as tetracycline, chloramphenicol, phenylboric acid, fusidic acid have been shown to inhibit the template-free synthesis of polypeptides. The synthesis requires GTP cleavage; a non-cleavable analog of GTP, guanyl-5′-yl methylenediphosphonate does not maintain the synthesis.Among sixteen different aminoacyl-tRNAs studied as substrates for the ribosomal template-free synthesis of polypeptides Lys-tRNA, Ser-tRNA, Thr-tRNA and Asp-tRNA were the best. Gly-tRNA, Glu-tRNA, Val-tRNA, Arg-tRNA, Ala-tRNA and Leu-tRNA as substrates gave relatively low levels of the polypeptide synthesis on non-programmed ribosomes. Pro-tRNA, Phe-tRNA, Asn-tRNA, Met-tRNA, Ile-tRNA and Gln-tRNA were practically inactive as substrates for the template-free elongation. No correlation has been found between the abilities of the aminoacyl-tRNAs to serve as substrates for the template-free elongation and their activities in template-free binding to ribosomes.     

Influence of the fermentative cross-seams on the structure of the microsomal membrane

In rat liver microsomes freezing with subsequent thawing led to irreversible redistribution of protein-lipid packing. This redistribution was detected by a change in the efficiency of energy transfer between protein aromatic groups of membrane protein and lipid-soluble fluorescent probe pyrene. Transglutaminase pretreatment of microsomes prevented the irreversible redistribution. The enzyme is shown to bind no more than 15 per cent of the whole membrane protein. This smaller part of the microsomal protein is supposed to play the decisive role in the movements of its remaining part.