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Domain V (domain + v)

Distribution by Scientific Domains

Medical Sciences	33%

Selected Abstracts

Domain V of m-calpain shows the potential to form an oblique-orientated ,-helix, which may modulate the enzyme's activity via interactions with anionic lipid

FEBS JOURNAL, Issue 22 2002
Klaus Brandenburg
The activity of m-calpain, a heterodimeric, Ca2+ -dependent cysteine protease appears to be modulated by membrane interactions involving oblique-orientated ,-helix formation by a segment, GTAMRILGGVI, in the protein's smaller subunit. Here, graphical and hydrophobic moment-based analyses predicted that this segment may form an ,-helix with strong structural resemblance to the influenza virus peptide, HA2, a known oblique-orientated ,-helix former. Fourier transform infrared spectroscopy showed that a peptide homologue of the GTAMRILGGVI segment, VP1, adopted low levels of ,-helical structure (, 20%) in the presence of zwitterionic lipid and induced a minor decrease (3 °C) in the gel to liquid-crystalline phase transition temperature, TC, of the hydrocarbon chains of zwitterionic membranes, suggesting interaction with the lipid headgroup region. In contrast, VP1 adopted high levels of ,-helical structure (65%) in the presence of anionic lipid, induced a large increase (10 °C) in the TC of anionic membranes, and showed high levels of anionic lipid monolayer penetration (,SP = 5.5 mN·m,1), suggesting deep levels of membrane penetration. VP1 showed strong haemolytic ability (LD50 = 1.45 mm), but in the presence of ionic agents, this ability, and that of VP1 to penetrate anionic lipid monolayers, was greatly reduced. In combination, our results suggest that m-calpain domain V may penetrate membranes via the adoption of an oblique-orientated ,-helix and electrostatic interactions. We speculate that these interactions may involve snorkelling by an arginine residue located in the polar face of this ,-helix. [source]

Platelet adhesion to dimeric ,2 -glycoprotein I under conditions of flow is mediated by at least two receptors: glycoprotein Ib, and apolipoprotein E receptor 2,

JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 2 2007
M. T. T. PENNINGS
Summary.,Background: The major antigen implicated in the antiphospholipid syndrome is beta2-glycoprotein I (,2GPI). Dimerized ,2GPI binds to apolipoprotein E receptor 2, (apoER2,) on platelets and increases platelet adhesion to collagen under conditions of flow. Aim: To investigate whether the interaction between dimerized ,2GPI and platelets is sufficiently strong to resist shear stresses. Methods: We studied the interaction of platelets with immobilized dimerized ,2GPI under conditions of flow, and further analyzed the interaction using surface plasmon resonance and solid phase immunoassays. Results: We found that dimerized ,2GPI supports platelet adhesion and aggregate formation under venous flow conditions. Adhesion of platelets to dimerized ,2GPI was completely inhibited by the addition of soluble forms of both apoER2, and GPIb,, and the addition of receptor-associated protein and the removal of GPIb, from the platelet surface. GPIb, co-precipitated with apoER2,, suggesting the presence of complexes between GPIb, and apoER2, on platelet membranes. The interaction between GPIb, and dimeric ,2GPI was of intermediate affinity (Kd = 180 nm) and Zn2+, but not Ca2+ -dependent. Deletion of domain V from dimeric ,2GPI strongly reduced its binding to both GPIb, and apoER2,. Antibodies that inhibit the binding of thrombin to GPIb, inhibited platelet adhesion to dimeric ,2GPI completely, while antibodies blocking the binding of von Willebrand factor to GPIb, had no effect. Dimeric ,2GPI showed reduced binding to low-sulfated GPIb, compared to the fully sulfated form. Conclusion: We show that platelets adhere to dimeric ,2GPI under both arterial and venous shear stresses. Platelets adhere via two receptors: GPIb, and apoER2,. These receptors are present in a complex on the platelet surface. [source]

Ribosome,DnaK interactions in relation to protein folding

MOLECULAR MICROBIOLOGY, Issue 6 2003
Jaydip Ghosh
Summary Bacterial ribosomes or their 50S subunit can refold many unfolded proteins. The folding activity resides in domain V of 23S RNA of the 50S subunit. Here we show that ribosomes can also refold a denatured chaperone, DnaK, in vitro, and the activity may apply in the folding of nascent DnaK polypeptides in vivo. The chaperone was unusual as the native protein associated with the 50S subunit stably with a 1:1 stoichiometry in vitro. The binding site of the native protein appears to be different from the domain V of 23S RNA, the region with which denatured proteins interact. The DnaK binding influenced the protein folding activity of domain V modestly. Conversely, denatured protein binding to domain V led to dissociation of the native chaperone from the 50S subunit. DnaK thus appears to depend on ribosomes for its own folding, and upon folding, can rebind to ribosome to modulate its general protein folding activity. [source]

The pleuromutilin drugs tiamulin and valnemulin bind to the RNA at the peptidyl transferase centre on the ribosome

MOLECULAR MICROBIOLOGY, Issue 5 2001
Susan M. Poulsen
The pleuromutilin antibiotic derivatives, tiamulin and valnemulin, inhibit protein synthesis by binding to the 50S ribosomal subunit of bacteria. The action and binding site of tiamulin and valnemulin was further characterized on Escherichia coli ribosomes. It was revealed that these drugs are strong inhibitors of peptidyl transferase and interact with domain V of 23S RNA, giving clear chemical footprints at nucleotides A2058,9, U2506 and U2584,5. Most of these nucleotides are highly conserved phylogenetically and functionally important, and all of them are at or near the peptidyl transferase centre and have been associated with binding of several antibiotics. Competitive footprinting shows that tiamulin and valnemulin can bind concurrently with the macrolide erythromycin but compete with the macrolide carbomycin, which is a peptidyl transferase inhibitor. We infer from these and previous results that tiamulin and valnemulin interact with the rRNA in the peptidyl transferase slot on the ribosomes in which they prevent the correct positioning of the CCA-ends of tRNAs for peptide transfer. [source]

Ro 60 functions as a receptor for ,2 -glycoprotein I on apoptotic cells

ARTHRITIS & RHEUMATISM, Issue 3 2009
Joanne H. Reed
Objective The autoantigens 60-kd Ro/SSA (Ro 60) and ,2 -glycoprotein I (,2GPI) are both displayed on the surface membrane of apoptotic cells. Epitope-spreading experiments have suggested that these autoantigens may be present as a complex on the apoptotic cell surface. This study was undertaken to investigate whether ,2GPI interacts with Ro 60 on apoptotic cells and alters the binding of anti,Ro 60 IgG. Methods The interaction between soluble recombinant Ro 60 fragments and ,2GPI was investigated in vitro by direct and saturation binding assays using native human ,2GPI and recombinant domain deletion mutants. Binding of ,2GPI to early and late apoptotic cells was assessed by multiparameter flow cytometry, and specificity of binding was determined by competitive inhibition with soluble recombinant Ro 60 and anti,Ro 60 IgG. Results The Ro 60 fragment expressing a surface-exposed epitope (apotope) bound with high affinity (Kd = ,15 nM) to domain V of ,2GPI in vitro. Beta2 -glycoprotein I bound to the surface of apoptotic cells in a dose-dependent manner and was blocked by the Ro 60 apotope fragment. In reciprocal competitive inhibition studies, ,2GPI blocked the binding of anti,Ro 60 autoantibodies to apoptotic cells in a dose-dependent manner, and anti,Ro 60 IgG inhibited the binding of ,2GPI. Moreover, ,2GPI showed a 2-fold increase in binding to apoptotic cells that overexpress Ro 60 on the surface. Conclusion These results demonstrate that Ro 60 functions as a novel receptor for ,2GPI on the surface of apoptotic cells. The formation of Ro 60,,2GPI complexes may protect against anti,Ro 60 autoantibody,mediated tissue injury. [source]