Antigen-specific, major histocompatability complexrestricted recognition by classical T cells is mediated by a T cell receptor (TCR) consisting of a disulfidelinked aj3 heterodimer. During the search for the genes encoding the a and /3 proteins, a third immunoglobulinlikegene, termed y, was uncovered. Like the 7CR a and /3genes, the TCR -ygene consistsof variable and constant segments that rear...

Mammalian globin gene expression is activated through NFthat encodes the human homolog of chicken MafG. Human MafG heterodimerizes with p45 NF-E2 and binds DNA with E2 elements recognized by basic-leucine zipper proteins of the AP-1 superfamily. The specificity of NF-E2 DNA binding specificity identical to that of purified NF-E2 DNA binding activity. A tethered heterodimer of p45 and MafG is fu...

Celiac disease (CD) is most probably an immunological disease, precipitated in susceptible individuals by ingestion of wheat gliadin and related proteins from other cereals. The disease shows a strong human HLA association predominantly to the cis or trans encoded HLA-DQ(alpha 1*0501,beta 1*0201) (DQ2) heterodimer. T cell recognition of gliadin presented by this DQ heterodimer may thus be of im...

Umami taste (corresponds to savory in English) is elicited by L-glutamate, typically as its Na salt (monosodium glutamate: MSG), and is one of five basic taste qualities that plays a key role in intake of amino acids. A particular property of umami is the synergistic potentiation of glutamate by purine nucleotide monophosphates (IMP, GMP). A heterodimer of a G protein coupled receptor, TAS1R1 a...

Factor VIII, a non-covalent heterodimer comprised of a heavy chain (A1-A2-B domains) and light chain (A3-C1-C2 domains), circulates as an inactive procofactor in complex with von Willebrand factor. Metal ions are critical to the integrity of factor VIII, with Cu and Ca ions stabilizing the heterodimer and generating the active conformation, respectively. Activation of factor VIII catalyzed by t...

Platelet membrane glycoproteins (GP) IIb and IIIa form a Ca2+-dependent, heterodimer complex (GP IIb-IIIa) in detergent solution. To determine whether these glycoproteins were complexed or dissociated in intact human platelets, 125I-labeled whole platelets were lysed with an EDTA/Triton X-100 buffer, which stabilized both the complexed and dissociated forms of GP IIb and GP IIIa. The percentage...

Acidic ribosomal phosphoproteins P0, P1 and P2 were isolated in soluble form from silkworm ribosomes and tested for their interactions with each other and with RNA fragments corresponding to the GTPase-associated domain of residues 1030-1127 (Escherichia coli numbering) in silkworm 28S rRNA in vitro. Mixing of P1 and P2 formed the P1-P2 heterodimer, as demonstrated by gel mobility shift and che...

Ultrafast singlet excited state energy transfer occurs from the monomeric chromophores to the primary electron donor or special pair in photosynthetic reaction centers. The mechanism of this process has been investigated using reaction centers whose special pair absorption is severely perturbed by removal of the Mg atom of one of the bacteriochlorophylls (the heterodimer mutant (M)H202L). This ...

The copper chaperone for superoxide dismutase (CCS) activates the antioxidant enzyme Cu,Zn-SOD (SOD1) by directly inserting the copper cofactor into the apo form of SOD1. Neither the mechanism of protein-protein recognition nor of metal transfer is clear. The metal transfer step has been proposed to occur within a transient copper donor/acceptor complex that is either a heterodimer or heterotet...

The molecular dynamics of nuclear protein import were examined in a solution binding assay by testing for interactions between a protein containing a nuclear localization signal (NLS), the transport factors karyopherin alpha, karyopherin beta, and Ran, and FXFG or GLFG repeat regions of nucleoporins. We found that karyopherins alpha and beta cooperate to bind FXFG but not GLFG repeat regions. B...