The 3' terminal forty nucleotides of tobraviral RNAs readily fold into a tertiary structure, resembling that of tymo- and tobamoviral RNAs. The latter RNAs possess a tRNA-like structure at their 3' end that is recognized by a number of tRNA-specific enzymes (Rietveld et al. (1984), EMBO J. 3, 2613-2619). Characteristic for their aminoacyl acceptor arm is the presence of a so-called pseudoknot which we now also find in a corresponding position at the 3' terminus of TRV RNA2 (PSG strain). The nucleotide sequences of all tobraviral RNAs analysed so far indicate that they all possess a similar 3' terminal structure. A domain resembling the anticodon arm of canonical tRNA is not readily recognizable. TRV RNA2 can be adenylated with CTP, ATP; tRNA nucleotidyl transferase and ATP. It is unable, however, to accept any of the twenty common amino acids when incubated with ATP and aminoacyl-tRNA synthetases from wheat germ or yeast. We conclude that TRV RNA contains a tRNA-like structure, which, in contrast to the tymo- and tobamoviral tRNA-like structures, cannot be aminoacylated. It is unlikely therefore, that aminoacylation of plant viral RNAs with a tRNA-like structure is a prerequisite for viral RNA replication.
The hydrodynamics of the bacterial elongation factor EF-Tu have been studied in the presence of its ligand guanosine-5'-diphosphate (GDP) by sedimentation in the ultracentrifuge and quasielastic light scattering. Sedimentation studies have made it possible to establish experimental conditions under which only negligible aggregation of the protein occurs (neutral pH, concentration less than 3 mg/mL). Analysis of the light intensity autocorrelation functions under these conditions revealed two independent scattering species with diffusion coefficients of 0.71 X 10(-6) and 0.04 X 10(-6) cm2 s-1. The material with the lower diffusion coefficient, i.e., the aggregates, represented less than 1% of the total number of EF-Tu particles. The other 99% diffused as monomeric molecules with a molar mass corresponding to the value calculated from the known primary structure of the protein. The hydrodynamic parameters derived from the experimental data suggest that EF-Tu.GDP in solution is close to a spherical particle.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.