Tetanus toxoid is a routine positive control antigen for cellular assays. Previous studies identified multiple tetanus toxin (TT) epitopes, including some 'universal' epitopes. However, rigorous HLA-restricted study of tetanus toxoid responses is still lacking. In this study, the tetramer-guided epitope mapping approach was used to identify CD4+ T-cell epitopes within the TT heavy chain restric...

Deoxygenation-dependent association of hemoglobin tetramers appears to be widespread among amphibians, reptiles, and possibly all or most birds. The evidence for this conclusion depends largely on oxygen equilibria of whole blood which have Hill coefficients that reach values as high as 5-7 at 80-90% oxygenation. Computer simulation of the sedimentation velocity behavior of the major components...

Efficient delivery of membrane proteins is a critical cellular process. The recently elucidated GET (Guided Entry of TA proteins) pathway is responsible for the targeted delivery of tail-anchored (TA) membrane proteins to the endoplasmic reticulum. The central player is the ATPase Get3, which in its free form exists as a dimer. Biochemical evidence suggests a role for a tetramer of Get3. Here, ...

Tissue-specific overexpression of the human systemic amyloid precursor transthyretin (TTR) ameliorates Alzheimer's disease (AD) phenotypes in APP23 mice. TTR-β-amyloid (Aβ) complexes have been isolated from APP23 and some human AD brains. We now show that substoichiometric concentrations of TTR tetramers suppress Aβ aggregation in vitro via an interaction between the thyroxine binding pocket of...

Nucleosomes uniquely positioned on high-affinity DNA sequences present a polar barrier to transcription by human and yeast RNA polymerase II (Pol II). In one transcriptional orientation, these nucleosomes provide a strong, factor- and salt-insensitive barrier at the entry into the H3/H4 tetramer that can be recapitulated without H2A/H2B dimers. The same nucleosomes transcribed in the opposite o...

The force-extension profile of tetrameric spectrin is determined by using multiscale computer simulation. Fluctuation results of atomistic simulations of double spectrin repeat units (DSRU) are used to systematically build a coarse-grained (CG) model for the tetrameric form of spectrin. It is found that the spectrin tetramer can be modeled as a soft polymer with a unique flat force-extension pr...

The greatly increased tetramer strength of liganded fetal hemoglobin compared with adult hemoglobin is shown by its 70-fold smaller tetramer-dimer dissociation constant. This property has been shown previously to be only partially caused by the 5-amino-acid differences at both types of interfaces in each hemoglobin. A major contributor to tetramer strengthening is the 18-amino-acid N-terminal A...

The description of unitary few-boson systems is conceptually simple: only one parameter -- the three-body binding energy required to predict energies clusters with an arbitrary number bosons. Whether this correlation between three- and many-boson still holds for two species bosons which inter-species interaction resonant depends on how many particles each are in system. For few-body $A$ $B$ a $...

The transthyretin (TTR) amyloid diseases are of keen interest, because there are >80 mutations that cause, and a few mutations that suppress, disease. The V122I variant is the most common amyloidogenic mutation worldwide, producing familial amyloidotic cardiomyopathy primarily in individuals of African descent. The substitution shifts the tetramer-folded monomer equilibrium toward monomer (lowe...

Preprotein translocase is a general and essential system for bacterial protein export, the minimal components of which are SecA and SecYEG. SecA is a peripheral ATPase that associates with nucleotide, preprotein, and the membrane integral SecYEG to form a translocation-competent complex. SecA can be separated into two domains: an N-terminal 68 kDa ATPase domain (N68) that binds preprotein and c...