Functional insights from the structure of the 30S ribosomal subunit and its interactions with antibiotics

The 30S ribosomal subunit has two primary functions in protein synthesis. It discriminates against aminoacyl transfer RNAs that do not match the codon of messenger RNA, thereby ensuring accuracy in translation of the genetic message in a process called decoding. Also, it works with the 50S subunit to move the tRNAs and associated mRNA by precisely one codon, in a process called translocation. Here we describe the functional implications of the high-resolution 30S crystal structure presented in the accompanying paper, and infer details of the interactions between the 30S subunit and its tRNA and mRNA ligands. We also describe the crystal structure of the 30S subunit complexed with the antibiotics paromomycin, streptomycin and spectinomycin, which interfere with decoding and translocation. This work reveals the structural basis for the action of these antibiotics, and leads to a model for the role of the universally conserved 16S RNA residues A1492 and A1493 in the decoding process.     

Microdeletion encompassing MAPT at chromosome 17q21.3 is associated with developmental delay and learning disability

Recently, the application of array-based comparative genomic hybridization (array CGH) has improved rates of detection of chromosomal imbalances in individuals with mental retardation and dysmorphic features. Here, we describe three individuals with learning disability and a heterozygous deletion at chromosome 17q21.3, detected in each case by array CGH. FISH analysis demonstrated that the deletions occurred as de novo events in each individual and were between 500 kb and 650 kb in size. A recently described 900-kb inversion that suppresses recombination between ancestral H1 and H2 haplotypes encompasses the deletion. We show that, in each trio, the parent of origin of the deleted chromosome 17 carries at least one H2 chromosome. This region of 17q21.3 shows complex genomic architecture with well-described low-copy repeats (LCRs). The orientation of LCRs flanking the deleted segment in inversion heterozygotes is likely to facilitate the generation of this microdeletion by means of non-allelic homologous recombination.     

EYS, encoding an ortholog of Drosophila spacemaker, is mutated in autosomal recessive retinitis pigmentosa

Using a positional cloning approach supported by comparative genomics, we have identified a previously unreported gene, EYS, at the RP25 locus on chromosome 6q12 commonly mutated in autosomal recessive retinitis pigmentosa. Spanning over 2 Mb, this is the largest eye-specific gene identified so far. EYS is independently disrupted in four other mammalian lineages, including that of rodents, but is well conserved from Drosophila to man and is likely to have a role in the modeling of retinal architecture.     

Diet and the evolution of human amylase gene copy number variation

Starch consumption is a prominent characteristic of agricultural societies and hunter-gatherers in arid environments. In contrast, rainforest and circum-arctic hunter-gatherers and some pastoralists consume much less starch. This behavioral variation raises the possibility that different selective pressures have acted on amylase, the enzyme responsible for starch hydrolysis. We found that copy number of the salivary amylase gene (AMY1) is correlated positively with salivary amylase protein level and that individuals from populations with high-starch diets have, on average, more AMY1 copies than those with traditionally low-starch diets. Comparisons with other loci in a subset of these populations suggest that the extent of AMY1 copy number differentiation is highly unusual. This example of positive selection on a copy number-variable gene is, to our knowledge, one of the first discovered in the human genome. Higher AMY1 copy numbers and protein levels probably improve the digestion of starchy foods and may buffer against the fitness-reducing effects of intestinal disease.     

Fast Implementation of Iterative Reconstruction with Exact Ray-Driven Projector on GPUs

Iterative methods are popular choices in image reconstruction fields due to their capability of recovering object information from incomplete acquisition data.However,the computation process involves frequent uses of forward and backward projections that are computationally expensive.Past research has proved that a forward projector that can produce high quality images is crucial to achieve a good convergence rate.In this paper a high performance iterative reconstruction framework is introduced,where two mo...     

Hydrogen bonding and biological specificity analysed by protein engineering

The role of complementary hydrogen bonding as a determinant of biological specificity has been examined by protein engineering of the tyrosyl-tRNA synthetase. Deletion of a side chain between enzyme and substrate to leave an unpaired, uncharged hydrogen-bond donor or acceptor weakens binding energy by only 0.5-1.5 kcal mol-1. But the presence of an unpaired and charged donor or acceptor weakens binding by a further approximately 3 kcal mol-1.     

The Bohr effect and the red cell 2–3 DPG and Hb content in sherpas and europeans at low and at high altitude

Riassunto Europei e Sherpas hanno mostrato, dopo una permanenza di 3–4 giorni ad una altitudine di circa 5000 metri, normali P₅₀ (a pH 7.4 ed a pH 6.8) ed effetto Bohr (molto variabile negli Europei) ed elevato contenuto ematico di 2–3 DPG.