420 research outputs found
Ubiquitination accomplished: E1 and E2 enzymes were not necessary
Qiu et al. (2016) show that a mono-ADP-ribosyltransferase, SdeA, from Legionella pneumophila catalyzes ADP-ribosylation of ubiquitin, allowing SdeA to modify substrate with ubiquitin in the absence of E1 and E2 enzymes
Renormalizability of Massive Gravity in Three Dimensions
We discuss renormalizability of a recently established, massive gravity
theory with particular higher derivative terms in three space-time dimensions.
It is shown that this massive gravity is certainly renormalizable as well as
unitary, so it gives us a physically interesting toy model of perturbative
quantum gravity in three dimensions.Comment: 13 pages, no figure
Analysis of IgE turnover in non-sensitized and sensitized rats.
BACKGROUND: Although the levels of immunoglobulin E (IgE) in the circulating blood are often elevated in patients with allergic diseases, such levels cannot always be considered as pathognomonic signs of allergy. The induction of allergic reactions in the tissue was inferred to be related to the amount of IgE passing through the vascular wall. AIMS: We attempted to clarify which compartment, the intravascular or extravascular, plays an important role in the regulation of the turnover of rat IgE. METHODS: The level of DNP-specific rat IgE in the serum was estimated by IgE-capture enzyme-linked immunosorbent assay, and the turnover of IgE was analyzed from its pharmacokinetic parameters. RESULTS: The transfer rate constants from the central to tissue compartment (Kct) were larger than those from the tissue to central compartment (Ktc) irrespective of the sensitized state. The value of the distribution volume of the tissue compartment (Vt) was larger than that of the distribution volume of the central compartment (Vc) irrespective of the sensitized state. CONCLUSIONS: These Findings suggest that the short half-life of rat IgE in the circulation could be attributable to the distribution of IgE from the intravascular to the extravascular compartment
Remarks on Higgs Mechanism for Gravitons
We construct two kinds of model exhibiting Higgs mechanism for gravitons in
potentials of scalar fields. One class of the model is based on a potential
which is a generic function of the induced internal metric , and the
other involves a potential which is a generic function of the usual metric
tensor and the induced curved metric . In the both
models, we derive conditions on the scalar potential in such a way that
gravitons acquire mass in a flat Minkowski space-time without non-unitary
propagating modes in the process of spontaneous symmetry breaking of
diffeomorphisms through the condensation of scalar fields. We solve the
conditions and find a general solution for the potential. As an interesting
specific solution, we present a simple potential for which the Higgs mechanism
for gravitons holds in any value of cosmological constant.Comment: 13 page
A general strategy for discovery of inhibitors and activators of RING and U-box E3 ligases with ubiquitin variants
RING and U-box E3 ubiquitin ligases regulate diverse eukaryotic processes and have been implicated in numerous diseases, but targeting these enzymes remains a major challenge. We report the development of three ubiquitin variants (UbVs), each binding selectively to the RING or U-box domain of a distinct E3 ligase: monomeric UBE4B, phosphorylated active CBL, or dimeric XIAP. Structural and biochemical analyses revealed that UbVs specifically inhibited the activity of UBE4B or phosphorylated CBL by blocking the E2∼Ub binding site. Surprisingly, the UbV selective for dimeric XIAP formed a dimer to stimulate E3 activity by stabilizing the closed E2∼Ub conformation. We further verified the inhibitory and stimulatory functions of UbVs in cells. Our work provides a general strategy to inhibit or activate RING/U-box E3 ligases and provides a resource for the research community to modulate these enzymes
Bending AdS Waves with New Massive Gravity
We study AdS-waves in the three-dimensional new theory of massive gravity
recently proposed by Bergshoeff, Hohm, and Townsend. The general configuration
of this type is derived and shown to exhibit different branches, with different
asymptotic behaviors. In particular, for the special fine tuning
, solutions with logarithmic fall-off arise, while in the
range , spacetimes with Schrodinger isometry group are admitted
as solutions. Solutions that are asymptotically AdS, both for
Brown-Henneaux and for the weakened boundary conditions, are also identified.
The metric function that characterizes the profile of the AdS-wave behaves as a
massive excitation on the spacetime, with an effective mass given by
. For the critical value , the value of
the effective mass precisely saturates the Breitenlohner-Freedman bound for the
AdS space where the wave is propagating on. The analogies with the AdS-wave
solutions of topologically massive gravity are also discussed. Besides, we
consider the coupling of both massive deformations to Einstein gravity and find
the exact configurations for the complete theory, discussing all the different
branches exhaustively. One of the effects of introducing the Chern-Simons
gravitational term is that of breaking the degeneracy in the effective mass of
the generic modes of pure New Massive Gravity, producing a fine structure due
to parity violation. Another effect is that the zoo of exact logarithmic
specimens becomes considerably enlarged.Comment: 9 pages. Minor typos correcte
Structure of UBE2K-Ub/E3/polyUb reveals mechanisms of K48-linked Ub chain extension
Ubiquitin (Ub) chain types govern distinct biological processes. K48-linked polyUb chains target substrates for proteasomal degradation, but the mechanism of Ub chain synthesis remains elusive due to the transient nature of Ub-handover. Here, we present the structure of a chemically trapped complex of E2 UBE2K covalently linked to donor Ub and acceptor K48-linked di-Ub, primed for K48-linked Ub chain synthesis by a RING E3. The structure reveals the basis for acceptor Ub recognition by UBE2K active site residues and the C-terminal Ub-associated (UBA) domain to impart K48-linked Ub specificity and catalysis. Furthermore, the structure unveils multiple Ub binding surfaces on the UBA domain that allow distinct binding modes for K48-linked and K63-linked Ub chains. This multivalent Ub binding feature serves to recruit UBE2K to ubiquitinated substrates to overcome weak acceptor Ub affinity and thereby promote chain elongation. These findings elucidate the mechanism of processive K48-linked polyUb chain formation by UBE2K
Three-dimensional black holes, gravitational solitons, kinks and wormholes for BHT massive gravity
The theory of massive gravity in three dimensions recently proposed by
Bergshoeff, Hohm and Townsend (BHT) is considered. At the special case when the
theory admits a unique maximally symmetric solution, a conformally flat space
that contains black holes and gravitational solitons for any value of the
cosmological constant is found. For negative cosmological constant, the black
hole is characterized in terms of the mass and the "gravitational hair"
parameter, providing a lower bound for the mass. For negative mass parameter,
the black hole acquires an inner horizon, and the entropy vanishes at the
extremal case. Gravitational solitons and kinks, being regular everywhere, are
obtained from a double Wick rotation of the black hole. A wormhole solution in
vacuum that interpolates between two static universes of negative spatial
curvature is obtained as a limiting case of the gravitational soliton with a
suitable identification. The black hole and the gravitational soliton fit
within a set of relaxed asymptotically AdS conditions as compared with the ones
of Brown and Henneaux. In the case of positive cosmological constant the black
hole possesses an event and a cosmological horizon, whose mass is bounded from
above. Remarkably, the temperatures of the event and the cosmological horizons
coincide, and at the extremal case one obtains the analogue of the Nariai
solution, . A gravitational soliton is also obtained
through a double Wick rotation of the black hole. The Euclidean continuation of
these solutions describes instantons with vanishing Euclidean action. For
vanishing cosmological constant the black hole and the gravitational soliton
are asymptotically locally flat spacetimes. The rotating solutions can be
obtained by boosting the previous ones in the plane.Comment: Talk given at the "Workshop on Gravity in Three Dimensions," 14-24
April 2009, ESI, Vienna. 30 pages, 6 figures. V2: minor changes and section 6
slightly improved. Last version for JHE
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