Crystal structures reveal how distinct sites on the cysteine desulfurase IscS bind two different sulfur-acceptor proteins, IscU and TusA, to transfer sulfur atoms for iron-sulfur cluster biosynthesis and tRNA thiolation.

(2014) Modification of the wobble uridine in bacterial and mitochondrial tRNAs reading NNA/NNG triplets of 2-codon boxes, RNA Biology, 11:12, 1495-1507

Modifying RNA enzymes are highly specific for substrate-rRNA or tRNA-and the target position. In Escherichia coli, there are very few multisite acting enzymes, and only one rRNA/tRNA dual-specificity enzyme, pseudouridine synthase RluA, has been identified to date. Among the tRNA-modifying enzymes, the methyltransferase responsible for the m 2 A synthesis at purine 37 in a tRNA set still remains unknown. m 2 A is also present at position 2503 in the peptidyl transferase center of 23S RNA, where it is introduced by RlmN, a radical S-adenosyl-L-methionine (SAM) enzyme. Here, we show that E. coli RlmN is a dual-specificity enzyme that catalyzes methylation of both rRNA and tRNA. The DrlmN mutant lacks m 2 A in both RNA types, whereas the expression of recombinant RlmN from a plasmid introduced into this mutant restores tRNA modification. Moreover, RlmN performs m 2 A 37 synthesis in vitro using a tRNA chimera as a substrate. This chimera has also proved useful to characterize some tRNA identity determinants for RlmN and other tRNA modification enzymes. Our data suggest that RlmN works in a late step during tRNA maturation by recognizing a precise 3D structure of tRNA. RlmN inactivation increases the misreading of a UAG stop codon. Since loss of m 2 A 37 from tRNA is expected to produce a hyperaccurate phenotype, we believe that the error-prone phenotype exhibited by the DrlmN mutant is due to loss of m 2 A from 23S rRNA and, accordingly, that the m 2 A2503 modification plays a crucial role in the proofreading step occurring at the peptidyl transferase center.

No abstract

The purpose of this study was to evaluate foot arch types of obese children and adolescents aged 9-16.5 years using both indirect and direct measures. Fifty-eight obese children/adolescents attending the paediatric endocrinology unit of the University Hospital "Lozano Blesa" in Zaragoza were selected as experimental subjects. Fifty-eight gender and age matched, normal-weight children/adolescents were selected as control subjects. To assess the medial longitudinal arch (MLA) height, which is used as a main reference for the diagnosis of flatfoot, footprints from both feet were collected (in both groups) and lateral weight-bearing radiographs of both feet were taken (of 49 of the 58 obese children). Footprint angle (FA) and the Chippaux-Smirak index (CSI) were calculated from the footprints. Talus-first metatarsal (TFMA) and calcaneal inclination angles (CIA) were obtained from lateral feet radiographs. In the normal-weight group, mean values of FA and CSI indicated a normal MLA. In the obese group, morphological flatfoot was identified. Comparison between both groups, by side and gender, showed a decrease of FA (p<0.001) and an increase of CSI (p<0.001) in obese subjects. Mean values of TFMA and CIA in the obese group indicated a lowering of the MLA. Obese children/adolescents between 9 and 16.5 years of age had significantly lower values of FA and higher CSI, related to a lower MLA. Radiographic parameters supported these findings and mean values were associated with a fall of this arch.