603 research outputs found
Frequency analysis of cytolytic T cell precursors (CTL-P) generated in vivo during lethal rabies infection of mice. I. Distinction of CTL-P with different interleukin 2 sensitivity
The aim of this study was to determine the number and state of activity of cytolytic T lymphocytes (CTL) and their precursors (CTL-P) present in vivo during the early stages of viral infection. The local response to lethal infection with rabies virus was used as a model system that is not accessible to analysis by secondary activation in vitro. The local response to alloantigen served as a control. Experimental protocols were established that allow frequency estimates of in vivo antigen-triggered CTL-P. Data allow a distinction between CTL-P activated in vivo by alloantigen and viral antigen with respect to their different capacity to utilize T cell growth factors (inter-leukins). In vivo alloantigen-primed CTL-P generate, in vitro, an active effector progeny in the presence of interleukins of xenogeneic origin, whereas the majority of virus-specific CTL-P, in spite of considerable expansion in vivo, fail to generate CTL in vitro unless antigen is added
Nonclassical binding of formylated peptide in crystal structure of the MHC class lb molecule H2-M3
AbstractH2-M3 is a class Ib MHC molecule of the mouse with a 104-fold preference for binding N-fonmylated peptides. To elucidate the basis of this unusual specificity, we expressed and crystallized a soluble form of M3 with a fonnylated nonamer peptide, fMYFINILTL, and determined the structure by X-ray crystallography. M3, refined at 2.1AËresolution, resembles class la MHC molecules in its overall structure, but differs in the peptide-binding groove. The A pocket, which usually accommodates the free N-terminus of a bound peptide, is closed, and the peptide Is shifted one residue, such that the P1 side chain is lodged in the B pocket. The formyl group Is coordinated by His-9 and a bound water on the floor of the groove
Recent development and perspectives of machines for lattice QCD
I highlight recent progress in cluster computer technology and assess status
and prospects of cluster computers for lattice QCD with respect to the
development of QCDOC and apeNEXT. Taking the LatFor test case, I specify a
512-processor QCD-cluster better than 1$/Mflops.Comment: 14 pages, 17 figures, Lattice2003(plenary
STRAIN DIFFERENCES IN THE EXPRESSION OF THE EPA-1-RESTRICTING ELEMENT
Epa-1-specific cytotoxic T lymphocytes (CTL) lyse epidermal cells (EC) of different Epa-1 + H-2 k strains, such as AKR, CBA, C58, and RF, at different levels. We used an H-2K k -specific monoclonal antibody (mAb) to test the hypothesis that this phenomenon is due to differences in the H-2-restricting element. Initially, we established the specificity of this mAb for the Epa-1-restricting element by demonstrating its capacity to inhibit the lysis of CBA EC by Epa-1-specific CTL. We then used it as the probe in a cellular radioimmunoassay to quantify the expression of the restricting element by EC of different H-2 k strains. We found that C58 and RF EC bound significantly less of the mAb than did CBA EC. Although AKR also bound less of the mAb than did CBA EC, the difference was not statistically significant. To examine the generality of this phenomenon, we quantified the expression of K k antigens on spleen cells (SC) of the same four strains. We found that RF SC, but not AKR or C58 SC, bound significantly less of the K k mAb than did CBA SC. Thus, the differential CTL lysis of Epa-1 + EC of different strains probably reflects differences in expression of the H-2-restricting element rather than of the nominal antigen.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75485/1/j.1744-313X.1987.tb00375.x.pd
Shear-Induced Unfolding Activates von Willebrand Factor A2 Domain for Proteolysis
To avoid pathological platelet aggregation by von Willebrand factor (VWF),
VWF multimers are regulated in size and reactivity for adhesion by
ADAMTS13-mediated proteolysis in a shear flow dependent manner. We examined if
tensile stress in VWF under shear flow activates the VWF A2 domain for cleavage
by ADAMTS13 using molecular dynamics simulations. We indeed observed stepwise
unfolding of A2 and exposure of its deeply buried ADAMTS13 cleavage site.
Interestingly, disulfide bonds in the adjacent and highly homologous VWF A1 and
A3 domains obstruct their mechanical unfolding. We generated a full length
mutant VWF featuring a homologous disulfide bond in A2 (N1493C and C1670S), in
an attempt to lock A2 against unfolding. We find this mutant to feature
ADAMTS13-resistant behavior in vitro. Our results yield molecular-detail
evidence for the force-sensoring function of VWF A2, by revealing how tension
in VWF due to shear flow selectively exposes the A2 proteolysis site to
ADAMTS13 for cleavage while keeping the folded remainder of A2 intact and
functional. We find the unconventional knotted Rossman fold of A2 to be the key
to this mechanical response, tailored for regulating VWF size and activity.
Based on our model we can explain the pathomechanism of some natural mutations
in the VWF A2 domain that significantly increase the cleavage by ADAMTS13
without shearing or chemical denaturation, and provide with the
cleavage-activated A2 conformation a structural basis for the design of
inhibitors for VWF type 2 diseases
Light emission from a scanning tunneling microscope: Fully retarded calculation
The light emission rate from a scanning tunneling microscope (STM) scanning a
noble metal surface is calculated taking retardation effects into account. As
in our previous, non-retarded theory [Johansson, Monreal, and Apell, Phys. Rev.
B 42, 9210 (1990)], the STM tip is modeled by a sphere, and the dielectric
properties of tip and sample are described by experimentally measured
dielectric functions. The calculations are based on exact diffraction theory
through the vector equivalent of the Kirchoff integral. The present results are
qualitatively similar to those of the non-retarded calculations. The light
emission spectra have pronounced resonance peaks due to the formation of a
tip-induced plasmon mode localized to the cavity between the tip and the
sample. At a quantitative level, the effects of retardation are rather small as
long as the sample material is Au or Cu, and the tip consists of W or Ir.
However, for Ag samples, in which the resistive losses are smaller, the
inclusion of retardation effects in the calculation leads to larger changes:
the resonance energy decreases by 0.2-0.3 eV, and the resonance broadens. These
changes improve the agreement with experiment. For a Ag sample and an Ir tip,
the quantum efficiency is 10 emitted photons in the visible
frequency range per tunneling electron. A study of the energy dissipation into
the tip and sample shows that in total about 1 % of the electrons undergo
inelastic processes while tunneling.Comment: 16 pages, 10 figures (1 ps, 9 tex, automatically included); To appear
in Phys. Rev. B (15 October 1998
Frequency analysis of cytolytic T cell precursors (CTL-P) generatedin vivo during lethal rabies infection of mice. I. Distinction of CTL-P with different interleukin 2 sensitivity
Transcription and mRNA export machineries SAGA and TREX-2 maintain monoubiquitinated H2B balance required for DNA repair
DNA repair is critical to maintaining genome integrity, and its dysfunction can cause accumulation of unresolved damage that leads to genomic instability. The SptâAdaâGcn5 acetyltransferase (SAGA) coactivator complex and the nuclear poreâassociated transcription and export complex 2 (TREX-2) couple transcription with mRNA export. In this study, we identify a novel interplay between human TREX-2 and the deubiquitination module (DUBm) of SAGA required for genome stability. We find that the scaffold subunit of TREX-2, GANP, positively regulates DNA repair through homologous recombination (HR). In contrast, DUBm adaptor subunits ENY2 and ATXNL3 are required to limit unscheduled HR. These opposite roles are achieved through monoubiquitinated histone H2B (H2Bub1). Interestingly, the activity of the DUBm of SAGA on H2Bub1 is dependent on the integrity of the TREX-2 complex. Thus, we describe the existence of a functional interaction between human TREX-2 and SAGA DUBm that is key to maintaining the H2B/HB2ub1 balance needed for efficient repair and HR
The Majority of H2-M3 Is Retained Intracellularly in a Peptide-Receptive State and Traffics to the Cell Surface in the Presence of N-Formylated Peptides
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