The structure of cat muscle pyruvate kinase.

The complete amino acid sequence of cat muscle pyruvate kinase has been determined and fitted to the 2.6 A resolution electron density map. Residues in the active site region are highly conserved in the cat muscle, chicken muscle, rat liver and yeast enzymes. The enzyme-bound magnesium, which is essential for activity, interacts with the side chain of glutamate-271 and with two main carbonyl groups. Lysine-269 is the probable acid/base catalyst responsible for the interconversion of pyruvate and enolpyruvate. A possible binding site for the essential monovalent cation is proposed.     

The complete amino acid sequence of adenylate kinase from baker's yeast

The complete amino acid sequence of cytosolic adenylate kinase (MgATP + AMP----MgADP + ADP) from baker's yeast has been determined. Tryptic and clostripaic cleavage of the protein yielded 27 and 10 fragments, respectively. They were sequenced with either a solid-phase sequencer or a gas-phase sequencer. Alignment of the clostripaic fragments was deduced from the sequence of peptides obtained by endoproteinase Lys-C and cyanogen bromide cleavages. The N-terminus is blocked by an acetyl group as shown by proton magnetic resonance. Carboxypeptidase A digestion of the whole protein showed that the C-terminal sequence is -Lys-Asn, in agreement with the sequence of peptides from tryptic, clostripaic and 2-iodosobenzoic acid cleavages. The enzyme is a monomer of 220 amino acids with Mr 24077. Comparison of the sequence of the cytosolic adenylate kinases from yeast and pig shows 25% identity with highly conserved segments in the putative active-site region of the enzyme. After position 111, however, there is an insertion of 32 residues in the yeast species, similar to the adenylate kinase and the GTP:AMP phosphotransferase from beef heart mitochondria.     

Structural relationships in the adenylate kinase family

The sequences of five distantly related adenylate kinases have been aligned. The local conservation of amino acids is discussed in the light of the known three-dimensional structure of one of the enzymes, the cytosolic isoenzyme 1 (AK1) from porcine muscle. The similarity profile outlines clearly the active site in the cleft of the spatial structure of AK1. The alignment reveals further that the enzyme family can be subdivided into small and large variants according to the presence or absence of a particular segment of about 30 residues in the middle of the chain. The extra segments of the large variants are strongly conserved.     

Studies of the interaction of the maltose-binding protein of Escherichia coli, a closed-groove binder, with 4,6-O-ethylidenemalto-oligosaccharides (dp 2-5) and its regioselective labelling with 3-azibutyl 1-thio-alpha-(6-3H)maltoside.

Four malto-oligosaccharides (dp 2-5), each with a 4,6-O-ethylidene group on the glucosyl unit at the non-reducing terminus, were synthesised and used to prove that the maltose-binding protein (MBP) of E. coli is a closed-groove binder. alpha-D-Glucosylation of 3-azibutyl 1-thio-alpha-D-(6-3H)glucopyranoside yielded a 3H-labelled, photolabile 1-thiomaltoside derivative that was used to chemically modify the binding site of MBP. The 3H-labelled peptide containing 83% of the total radioactivity, which was isolated after tryptic cleavage of the modified MBP and sequenced, is part of the closed end of the MBP groove.     

Paired sequence difference in ribosomal RNAs: evolutionary and phylogenetic implications

Ribosomal RNAs have secondary structures that are maintained by internal Watson-Crick pairing. Through analysis of chordate, arthropod, and plant 5S ribosomal RNA sequences, we show that Darwinian selection operates on these nucleotide sequences to maintain functionally important secondary structure. Insect phylogenies based on nucleotide positions involved in pairing and the production of secondary structure are incongruent with those constructed on the basis of positions that are not. Furthermore, phylogeny reconstruction using these nonpairing bases is concordant with other, morphological data.      

Discovery of a novel class of potent and selective tetrahydroindazole-based sigma-1 receptor ligands

The sigma-1 and sigma-2 receptors have been shown to play important roles in CNS diseases, cancer, and other disorders. These findings suggest that targeting these proteins with small-molecule modulators may be of important therapeutic value. Here we report the development of a new class of tetrahydroindazoles that are highly potent and selective ligands for sigma-1. Molecular modeling was used to rationalize the observed structure-activity relationships and identify key interactions responsible for increased potency of the optimized compounds. Assays for solubility and microsomal stability showed this series possesses favorable characteristics and is amenable to further therapeutic development. The compounds described herein will be useful in the development of new chemical probes for sigma-1 and to aid in future work therapeutically targeting this protein.     

Training early visuo-spatial abilities: A controlled classroom-based intervention study

Visuo-spatial training is considered a promising approach to provide young children with a sound foundation for later mathematical learning. We developed and implemented a tablet-based visuo-spatial intervention in kindergarten classrooms aiming to foster the development of children’s visuo-spatial and numerical abilities. A sample of N?=?125 children participated in the present study, 68 children were part of the intervention group and participated in 20 training sessions of 20?min over a 10-week period, 57 children formed a business as usual control group. Results show that, at this young age, visuo-spatial and early math skills are already strongly interlinked. However, the training effects were domain-specific as they only improved visuo-spatial skills, but did not transfer to early math performance in the present setting.