F. Cramer

Über das aminoacylierungsverhalten chemisch modifizierter phenylalaninspezifischer transfer-ribonucleinsäure aus hefe: (1) Glykolspaltung und reduktion zum diol an der 3′-terminalen ribose

The terminal cis‐glycol‐group of phenylalanine specific tRNA (tRNAPhe, I) from yeast was oxidized to the dialdehyde by NaIO4 (tRNAPhe oxi, II) and subsequently reduced to the diol by NaBH4 (tRNAPhe oxi‐red, III). In charging experiments it could be shown that tRNAPhe oxi‐red is still completely specific for phenylalanine. The Michaelis constant of tRNAPhe oxi‐red remains unchanged when compared with tRNAPhe, while the maximun velocity of charging υmax of tRNAPhe oxi‐red is decreased to about one half.

Aminoacyl-tRNA synthetases from baker's yeast: reacting site of enzymatic aminoacylation is not uniform for all tRNAs.

In previous work we showed that tRNAPhe from baker’s yeast was phenylalanylated exclusively at the 2’hydroxyl group of the terminal ribose by phenylalanyl-tRNA synthetase [ 1,2]. This was based on the observation that after incorporation of 3’deoxyadenosine and 2’deoxyadenosine, respectively, into the terminus of tRNAPhe only tRNAPhe-C-C-3’dA could be aminoacylated whereas tRNAPhe-C-C-2’dA was a competitive inhibitor of the enzyme. The same result was later obtained, by an independent method, for tRNAPhe from Escherichiu coli and from rat liver [3]. These results seemed to be reasonable also from the chemical point of view as suggested by Zamecnik [4] since the 2’hydroxyl group is generally more reactive towards acylation. We then tested tRNAne, tRNASeT*, tRNATvr, and tRNAVa’ from yeast in order to check the general validity of the enzymatic aminoacylation of the more reactive 2’hydroxyl group. We found, however, three classes of tRNAs: those aminoacylated at the 2’hydroxyl group, those aminoacylated at the 3’hydroxyl group and those aminoacylatable at both hydroxyl groups. 2. Materials and methods

Methylation of elongation factor 1α in mouse 3T3B and 3T3BSV40 cells

Two‐dimensional gel electrophoretic (NEPHGE) analysis of proteins from mouse 3T3B and 3T3B/SV40 cells labelled with [methyl‐3H]methionine in the presence of cycloheximide have revealed that the elongation factor 1α (EF‐1α) in these cells is methylated and that the extent of methylation is higher in the SV40 transformed cell type. It is suggested that methylation may account for differences in growth properties for the different cell types.

Crystallization of yeast phenylalanine transfer ribonucleic acid

Abstract Two crystalline forms of yeast phenylalanine transfer RNA have been prepared from water-2-methylpentan-2,4-diol and water-tertiary butanol systems. One of the crystal forms has also been produced by the vapour phase method from water-dioxane and both have been produced by precipitation at a waterbutanol-2 interface. One crystal form is orthorhombic (space group C2221, density 1.47), a = 60.5 A , b = 85 A , c = 234 A and has 32 molecules in the unit cell, i.e. four molecules in the asymmetric unit, and the other is a rhombohedral form (space group R32, density 1.51), a rh = 124 A , α rh = 60.8 ° with 36 molecules in the unit cell, i.e. six molecules in the asymmetric unit. Data were collected to a resolution of 15 A with the orthorhombic crystals and to 7 A with the rhombohedral crystals. The orthorhombic form has a large mosaic spread. The crystals are stable. Yeast phenylalanine transfer RNA recovered from the crystals is chargeable to the same extent as the starting material.

Identification of elongation factor 1α from mouse liver

The bacterial protein elongation factors EF-Tu, EF-Ts and EF-G [l] are thought to have corresponding protein activities in eukaryotic cells now usually named EF-la, EFl/Z? and EF-2, respectively. Preparations of EF-la, the factor that carries aminoacyl-tRNA to the ribosome, have been obtained in various degrees of purity and activity from pig liver [2], rabbit reticulocytes [3], Artemia salina (brine shrimp) [4], yeast [5] and the fungus Mucor (61. In this laboratory, we have recently begun an investigation of possible changes occurring in cellular enzymes during ageing [7-91, with particular reference to the enzymes involved in the translational apparatus. EF-Tu is a major protein in E. coli [lo] as is EF-la in rabbit reticulocytes [ 111. Interestingly, a decrease in the specific activity of EF-la with age has been reported for Turbatrix aceti [ 121 and for rat liver and brain [ 131. Whether this change in specific activity is concomitant with a change in rate of synthesis or degradation or modification is as yet unknown. We are employing a combination of two-dimensional gel electrophoresis, SDS-PAGE and immunoblotting techniques to detect any alterations in the size or charge of EF-lar which may occur in this respect [ 141. Here we report the localisation of EF1 (Y on twodimensional gels using immunoblotting and the correlation of this information with currently available catalogues of mouse and human proteins [ 15,161. Immunoblotting Protein cataloguing