tRNA-Dependent Active Site Assembly in a Class I Aminoacyl-tRNA Synthetase

AbstractThe crystal structure of ligand-free E. coli glutaminyl-tRNA synthetase (GlnRS) at 2.4 Å resolution shows that substrate binding is essential to construction of a catalytically proficient active site. tRNA binding generates structural changes throughout the enzyme, repositioning key active site peptides that bind glutamine and ATP. The structure gives insight into longstanding questions regarding the tRNA dependence of glutaminyl adenylate formation, the coupling of amino acid and tRNA selectivities, and the roles of specific pathways for transmission of tRNA binding signals to the active site. Comparative analysis of the unliganded and tRNA-bound structures shows, in detail, how flexibility is built into the enzyme architecture and suggests that the induced-fit transitions are a key underlying determinant of both amino acid and tRNA specificity

Prokrastinasi Akademik dan Dukungan Sosial Teman Sebaya pada Mahasiswa Fakultas Psikologi Universitas Katolik Widya Mandala Surabaya

Prokrastinasi akademik merupakan perilaku penundaan yang dilakukan secara sengaja ketika memulai atau mengakhiri suatu tugas dengan tujuan menghindari kesulitan pada bidang akademik, seperti skripsi, yang berdampak keterlambatan pengumpulan tugas dan kelulusan bagi pelaku prokrastinasi. Salah satu faktor eksternal yang mempengaruhi prokrastinasi akademik adalah dukungan sosial. Untuk itu, penelitian ini bertujuan untuk mengetahui ada-tidaknya hubungan antara dukungan sosial teman sebaya dan prokrastinasi akademik pada mahasiswa Fakultas Psikologi Universitas Katolik Widya Mandala Surabaya. Subjek penelitian ialah mahasiswa Fakultas Psikologi Universitas Katolik Widya Mandala Surabaya (N=30) yang menempuh proposal skripsi atau skripsi lebih dari 1 semester. Teknik sampling yang digunakan ialah incidental sampling. Skala dalam penelitian ini terdiri dari dua skala yaitu skala prokrastinasi akademik dan skala dukungan sosial teman sebaya. Data yang diperoleh dianalisis menggunakan teknik analisis statistik non parametrik Kendall's Tau b. Hasil pengolahan statistik memperoleh koefisien korelasi sebesar 0,290 dengan nilai p sebesar 0,028 ( p≤0,05). Dapat disimpulkan bahwa ada hubungan positif antara prokrastinasi akademik dan dukungan sosial teman sebaya pada mahasiswa Fakultas Psikologi Universitas Katolik Widya Mandala Surabaya. Kata kunci: Prokrastinasi akademik, dukungan sosial teman sebay

An Algorithm to Find All Identical Motifs in Multiple Biological Sequences

Sequence motifs are of greater biological importance in nucleotide and protein sequences. The conserved occurrence of identical motifs represents the functional significance and helps to classify the biological sequences. In this paper, a new algorithm is proposed to find all identical motifs in multiple nucleotide or protein sequences. The proposed algorithm uses the concept of dynamic programming. The application of this algorithm includes the identification of (a) conserved identical sequence motifs and (b) identical or direct repeat sequence motifs across multiple biological sequences (nucleotide or protein sequences). Further, the proposed algorithm facilitates the analysis of comparative internal sequence repeats for the evolutionary studies which helps to derive the phylogenetic relationships from the distribution of repeats. © 2010 Springer-Verlag

Basal ganglia dysfunction in OCD: subthalamic neuronal activity correlates with symptoms severity and predicts high-frequency stimulation efficacy

Functional and connectivity changes in corticostriatal systems have been reported in the brains of patients with obsessive–compulsive disorder (OCD); however, the relationship between basal ganglia activity and OCD severity has never been adequately established. We recently showed that deep brain stimulation of the subthalamic nucleus (STN), a central basal ganglia nucleus, improves OCD. Here, single-unit subthalamic neuronal activity was analysed in 12 OCD patients, in relation to the severity of obsessions and compulsions and response to STN stimulation, and compared with that obtained in 12 patients with Parkinson's disease (PD). STN neurons in OCD patients had lower discharge frequency than those in PD patients, with a similar proportion of burst-type activity (69 vs 67%). Oscillatory activity was present in 46 and 68% of neurons in OCD and PD patients, respectively, predominantly in the low-frequency band (1–8 Hz). In OCD patients, the bursty and oscillatory subthalamic neuronal activity was mainly located in the associative–limbic part. Both OCD severity and clinical improvement following STN stimulation were related to the STN neuronal activity. In patients with the most severe OCD, STN neurons exhibited bursts with shorter duration and interburst interval, but higher intraburst frequency, and more oscillations in the low-frequency bands. In patients with best clinical outcome with STN stimulation, STN neurons displayed higher mean discharge, burst and intraburst frequencies, and lower interburst interval. These findings are consistent with the hypothesis of a dysfunction in the associative–limbic subdivision of the basal ganglia circuitry in OCD's pathophysiology

Structural conservation of an ancient tRNA sensor in eukaryotic glutaminyl-tRNA synthetase

In all organisms, aminoacyl tRNA synthetases covalently attach amino acids to their cognate tRNAs. Many eukaryotic tRNA synthetases have acquired appended domains, whose origin, structure and function are poorly understood. The N-terminal appended domain (NTD) of glutaminyl-tRNA synthetase (GlnRS) is intriguing since GlnRS is primarily a eukaryotic enzyme, whereas in other kingdoms Gln-tRNAGln is primarily synthesized by first forming Glu-tRNAGln, followed by conversion to Gln-tRNAGln by a tRNA-dependent amidotransferase. We report a functional and structural analysis of the NTD of Saccharomyces cerevisiae GlnRS, Gln4. Yeast mutants lacking the NTD exhibit growth defects, and Gln4 lacking the NTD has reduced complementarity for tRNAGln and glutamine. The 187-amino acid Gln4 NTD, crystallized and solved at 2.3 Å resolution, consists of two subdomains, each exhibiting an extraordinary structural resemblance to adjacent tRNA specificity-determining domains in the GatB subunit of the GatCAB amidotransferase, which forms Gln-tRNAGln. These subdomains are connected by an apparent hinge comprised of conserved residues. Mutation of these amino acids produces Gln4 variants with reduced affinity for tRNAGln, consistent with a hinge-closing mechanism proposed for GatB recognition of tRNA. Our results suggest a possible origin and function of the NTD that would link the phylogenetically diverse mechanisms of Gln-tRNAGln synthesis

Crystal Structure Analysis Reveals Functional Flexibility in the Selenocysteine-Specific tRNA from Mouse

Selenocysteine tRNAs (tRNA(Sec)) exhibit a number of unique identity elements that are recognized specifically by proteins of the selenocysteine biosynthetic pathways and decoding machineries. Presently, these identity elements and the mechanisms by which they are interpreted by tRNA(Sec)-interacting factors are incompletely understood.We applied rational mutagenesis to obtain well diffracting crystals of murine tRNA(Sec). tRNA(Sec) lacking the single-stranded 3'-acceptor end ((ΔGCCA)RNA(Sec)) yielded a crystal structure at 2.0 Å resolution. The global structure of (ΔGCCA)RNA(Sec) resembles the structure of human tRNA(Sec) determined at 3.1 Å resolution. Structural comparisons revealed flexible regions in tRNA(Sec) used for induced fit binding to selenophosphate synthetase. Water molecules located in the present structure were involved in the stabilization of two alternative conformations of the anticodon stem-loop. Modeling of a 2'-O-methylated ribose at position U34 of the anticodon loop as found in a sub-population of tRNA(Sec)in vivo showed how this modification favors an anticodon loop conformation that is functional during decoding on the ribosome. Soaking of crystals in Mn(2+)-containing buffer revealed eight potential divalent metal ion binding sites but the located metal ions did not significantly stabilize specific structural features of tRNA(Sec).We provide the most highly resolved structure of a tRNA(Sec) molecule to date and assessed the influence of water molecules and metal ions on the molecule's conformation and dynamics. Our results suggest how conformational changes of tRNA(Sec) support its interaction with proteins

Review of Aeroelasticity Testing Technology

AbstractAeroelasticity is the study of the mutual interaction that takes place among the inertial, elastic and aerodynamic forces acting on the structural members exposed to an airstream and the influence of this study on the design. This review paper deals with the investigation of the aeroelasticity phenomena. The effect of the aeroelasticity phenomena occurring while designing the wing of the aircraft are stated in detail. Flutter suppression and its techniques are investigated in this paper. The aeroelastic testing techniques available in this field and the efficient methods to solve these problems are discussed. The aeroelastic optimization techniques processes are reported. The fluid and structure interaction of the non-linear flexible wing structure results have been discussed for the various methods. The application of the MSC software and finite element methods are discussed. The aeroelastic applications are also summarize