Molecular characterization of a murine, major A/B type hnRNP protein: mBx

Journal URL: http://www.sciencedirect.com/science/journal/0167478

The contribution of the zinc-finger motif to the function of Thermus thermophilus ribosomal protein S14

In the crystal structure of the 30S ribosomal subunit from Thermus thermophilus, cysteine 24 of ribosomal protein S14 (TthS14) occupies the first position in a CXXC-X12-CXXC motif that coordinates a zinc ion. The structural and functional importance of. cysteine 24, which is widely conserved from bacteria to humans, was studied by its replacement with serine and by incorporating the resulting mutant into Escherichia coli ribosomes. The capability of such modified ribosomes in binding tRNA at the P and A-sites was equal to that obtained with ribosomes incorporating wild-type TthS14. In fact, both chimeric ribosomal species exhibited 20% lower tRNA affinity compared with native E. coli ribosomes. In addition, replacement of the native E. coli S14 by wild-type, and particularly by mutant TthS14, resulted in reduced capability of the 30S subunit for association with 50S subunits. Nevertheless, ribosomes from transformed cells sedimented normally and had a full complement of proteins. Unexpectedly, the peptidyl transferase activity in the chimeric ribosomes bearing mutant TthS14 was much lower than that measured in ribosomes incorporating wild-type TthS14. The catalytic center of the ribosome is located within the 50S subunit and, therefore, it is unlikely to be directly affected by changes in the structure of S14. More probably, the perturbing effects of S14 mutation on the catalytic center seem to be propagated by adjacent intersubunit bridges or the P-site tRNA molecule, resulting in weak donor-substrate reactivity. This hypothesis was verified by molecular dynamics simulation analysis. (C) 2007 Elsevier Ltd. All rights reserved

Force measurements of the disruption of the nascent polypeptide chain from the ribosome by optical tweezers

We show that optical tweezers are a valuable tool to study the co-translational folding of a nascent polypeptide chain at the ribosome in real-time. The aim of this study was to demonstrate that a stable and intact population of ribosomes can be tethered to polystyrene beads and that specific hook-ups to the nascent polypeptide chain by dsDNA handles, immobilized on a second bead, can be detected. A rupture force of the nascent chain in the range of 10-50 pN was measured, which demonstrates that the system is anchored to the surface in a stable and specific way. This will allow in numerous future applications to follow protein folding using much lower forces

Natural agents against neutrophil involvement in H.Pylori induced chronic gastritis

Helicobacter pylori infection is one of the widely spread human infections and the major risk for peptic ulcer disease, and gastric cancer and cause for chronic gastric inflammation. The major virulence factors in the development of gastric inflammation are VacA, CagA and HPNAP. HPNAP stimulates the production of reactive oxygen intermediates (ROIs) of human neutrophils and monocytes and promotes neutrophil adhesion to endothelial cells thereby causing mucosal damage. Agents (natural or chemical) inhibiting the HPNAP mediated neutrophil activation might be of great medical importance. According to current published data infiltration of neutrophils and mononuclear cells is significantly decreased due to CAPE mediated NF-kB suppression. In addition, according to our previous investigations AGPs, isolated from Pistacia lentiscus var Chia, inhibit neutrophil activation as well as neutrophil adhesion to endothelial cells. The emerging resistance of H.pylori to antibiotic treatment which provokes treatment failure and re-infection necessitates the investigation towards new forms of prevention and therapy of H.pylori induced chronic gastritis. © 2010 Nova Science Publishers, Inc. All rights reserved