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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The single-copy Drosophila muscle myosin heavy-chain (MHC) gene, located at 36B(2L), has a complex exon structure that produces a diversity of larval and adult muscle MHC isoforms through regulated alternative RNA splicing. Genomic and cDNA sequence analyses revealed that this 21-kilobase MHC gene encodes these MHC isoforms in 19 exons. However, five sets of these exons, encoding portions of the S1 head and the hinge domains of the MHC protein, are tandemly repeated as two, three, four, or five divergent copies, which are individually spliced into RNA transcripts. RNA hybridization studies with exon-specific probes showed that at least 10 of the 480 possible MHC isoforms that could arise by alternative RNA splicing of these exons are expressed as MHC transcripts and that the expression of specific members of alternative exon sets is regulated, both in stage and in muscle-type specificity. This regulated expression of specific exons is of particular interest because the alternatively spliced exon sets encode discrete domains of the MHC protein that likely contribute to the specialized contractile activities of different Drosophila muscle types. The alternative exon structure of the Drosophila MHC gene and the single-copy nature of this gene in the Drosophila genome make possible transgenic experiments to test the physiological functions of specific MHC protein domains and genetic and molecular experiments to investigate the mechanisms that regulate alternative exon splicing of MHC and other muscle gene transcripts.
Mol Cell Biol 1989 Jul
PMID:Functional domains of the Drosophila melanogaster muscle myosin heavy-chain gene are encoded by alternatively spliced exons. 250 34

Two bovine immunoglobulin constant region gamma heavy chain germline gene sequences are described. A gamma 1 gene was cloned from a lambda 2001 calf liver library screened with a human gamma 4 (pBRH4.1) probe and is contained in a 5.8 kb BamH1 hybridizing fragment. The gamma 2 gene was from an EMBL4 lambda library and is in a 6.6 kb BamH1 fragment. Each of these genes is arranged in four exons corresponding to the three CH domains and the hinge of gamma heavy chain genes; normal RNA splice and polyadenylation sites are present. The translated C-terminal peptide sequences of the genes match exactly the equivalent peptide sequences of bovine IgG1 and IgG2 heavy chains, identifying them as gamma 1 and gamma 2. The derived protein sequences reveal 96, 80 and 83% identity of amino acid residues between their CH1, CH2 and CH3 domains. Two adjacent cysteine residues encoded in the CH1 exons suggest that, as in rabbit gamma, an extra intra-chain disulphide bond occurs in the bovine gamma heavy chains. Significant DNA rearrangement in the hinge-CH2 region is evident in the bovine gamma 2 gene, with resultant deletion and substitution of amino acid residues in the lower hinge and N-terminal portion of the CH2 domain. The Fab-Fc interface of bovine IgG2 is predicted to be sterically blocked, relative to IgG1, which has implications for effector differences between the bovine gamma subclasses.
Mol Immunol 1989 Sep
PMID:Structure of bovine immunoglobulin constant region heavy chain gamma 1 and gamma 2 genes. 251 87

Mouse monoclonal antibody is not well fitted to destroying tumour cell targets. Complement and cellular effectors are inefficiently recruited, the cells can undergo antigenic modulation, antigen-negative mutants can arise, and the tumour-bearing subject can amount an immune response against the therapeutic antibody. This paper describes the preparation of two chimeric antibody derivatives designed to cirvumvent some of these problems. The first derivative is FabFc, prepared by linking Fab' gamma from monoclonal antibody to Fc gamma from human IgG. The bismaleimide linking agent forms a thioether bond with an SH group released by reduction of SS bonds in the hinge of each constituent. The second derivative is bisFabFc, formed by a bismaleimide in this case joining two FabFc molecules via a free SH in the Fc hinge of each. As regards antibody activity against target cells bisFabFc can be univalent (one active, one inactive Fab arm), bivalent, or bispecific (with each Fab arm directed against a different cell surface antigen). Its juxtaposed dual Fc regions are designed to promote cooperative binding of effectors. Some preliminary characterization in vitro has employed antibodies of anti-idiotypic specificity directed against guinea-pig L2C leukaemic B lymphocytes. The parent mouse IgG1 antibody failed to invoke complement cytotoxicity or antibody-dependent cellular cytotoxicity, while the chimeric derivatives yielded good killing in both systems. In complement lysis bivalent bicFabFc outperformed univalent, which in turn outperformed the FabFc monomer.
Mol Cell Biochem
PMID:Attack on neoplastic cell membranes by therapeutic antibody. 262 56

Interaction of jacalin, an N-terminal galactose specific lectin, with human IgA1 and IgA1 fragments was investigated. IgA1 and all galactose containing fragments bound to jacalin-Sepharose, including Fab fragments containing only the galNac linked to serine-224 and Fc fragments containing four gal-galNac sequences. These data indicate that both the galNac and gal-galNac sequences can interact with jacalin. Jacalin precipitated IgA1 and the fragments F(abc)2, F(ab')2 and Fc in agar gel and from solutions. It also precipitated Fab' fragments in agar gel. Jacalin did not precipitate Fab fragments significantly. This suggests that, except for the single binding site on the Fab fragments containing the galNac linked to serine-224, jacalin itself also has a limited number of sites to interact with N-terminal galactose residues. ELISA studies revealed that intact IgA1 had a lower jacalin binding capacity than F(abc)2 fragments which lack CH3 domains, than F(ab')2 which lack the CH2 and CH3 domains, and than Fc fragments containing four gal-galNac sequences. This led to the conclusion that part of the galNac or gal-galNac sequences in intact IgA1 molecules are inaccessible to interaction with jacalin. Cleaving the C-terminal domains off may have induced a reorientation of the hinge region structure, including the orientation of the carbohydrate units.
Mol Immunol 1989 Mar
PMID:Binding of human IgA1 and IgA1 fragments to jacalin. 270 75

A synthetic 18-amino acid peptide (Cys500-Lys517) was used to raise polyclonal antibodies in rabbits to the glucocorticoid receptor (GR). The sequence of this peptide is identical to that of residues 500-517 of the rat and 481-498 of the human GR. This sequence overlaps the carboxy-terminal end of the core DNA-binding domain and the amino-terminus of the hinge region of the receptor. Antiserum (AP64) was obtained which recognized both human and rat GR, as determined by immunoblots of receptors immunopurified with authentic anti-GR antibodies, immunoadsorption of both specific [3H]dexamethasone-bound GR and 98K receptors that were specifically covalently labeled by [3H]dexamethasone mesylate, and AP64-induced shifts in the elution position of monomeric [3H]dexamethasone-bound GR from Sephacryl S-300. The specificity of AP64 was demonstrated by the ability of the immunizing peptide, but not a peptide of similar length, to inhibit both the antibody-induced change in elution position from Sephacryl S-300 and the antibody-mediated immobilization of [3H]dexamethasone-bound complexes by protein-A. Further studies indicated that AP64 did not react with native steroid-free GR or with steroidbound (or affinity-labeled) unactivated GR, but did selectively associated with monomeric activated, steroid-bound (or affinity labeled) complexes. AP64 also inhibited the DNA binding of activated complexes in a manner that was specifically blocked by the immunizing peptide. Collectively, these data allow the direct localization of a structural region of the GR that is occluded in the unactivated complex but exposed as a result of activation.
Mol Endocrinol 1989 Feb
PMID:Region-specific antiglucocorticoid receptor antibodies selectively recognize the activated form of the ligand-occupied receptor and inhibit the binding of activated complexes to deoxyribonucleic acid. 271 Jan 32

Co-operative association, in which a protein subunit is held simultaneously by two bonds, is enormously more favorable than association forming either bond alone. A theoretical framework for calculating the effect of co-operativity is developed here, which should have a broad application to protein-protein and protein-DNA associations. The theory is applied in detail to actin. Fragmentation of an actin filament is extremely unfavorable: the association constant for annealing-fragmentation is estimated here to be at least 10(13) M-1. In contrast to these very strong bonds within the filament, subunits are loosely attached at the end, with an association constant of 2 x 10(5) M-1. The eight orders of magnitude difference between annealing-fragmentation and end association can be attributed to the co-operative formation of one additional protein-protein bond in the annealing reaction. This observation, and a quantitative analysis of the co-operativity, lead to an important conclusion: the longitudinal bond, which connects subunits in the long-pitch helix, must be substantially stronger than the diagonal bond, which connect subunits between these helices. This conclusion contradicts some recent models based on Fourier construction, in which the longitudinal bond is weak or absent. Prominent longitudinal bonds also require a rigidity of the actin filament that must be reconciled with previous reports of torsional flexibility. A hinge within the actin subunit is suggested, separating it into two flexibly attached domains. In one possible model the two domains are oriented radially: the inner domains are connected by longitudinal and diagonal bonds to form a relatively rigid helical backbone, and the outer domains are attached to this backbone by flexible hinges, permitting them to move through angles of 10 degrees to 20 degrees or more. Flexibility of the outer, myosin-binding domain should be functionally important, permitting attachment of myosin cross-bridges over a range of angles.
J Mol Biol 1989 Apr 05
PMID:Co-operativity in protein-protein association. The structure and stability of the actin filament. 271 58

We have studied the distortions induced in double-stranded oligonucleotides by covalently bound acetylaminofluorene residues and by apurinic sites. Within the acetylaminofluorene-modified oligonucleotide three base-pairs are unpaired as detected by the chemical probes chloroacetaldehyde and osmium tetroxide. These two probes reveal that the bases adjacent to the apurinic site are paired. In both the modified double-stranded oligonucleotides, the backbone on the 5' side of the modification is more reactive with 1,10-phenanthroline copper than the backbone on the 3' side. On polyacrylamide gels, the ligated multimers of acetylaminofluorene or apurinic site-modified oligonucleotides migrate slower than the multimers of the unmodified oligonucleotides. It is suggested that the acetylaminofluorene-modified guanine residues and the apurinic sites behave more as hinge joints than as the centres of directed bends.
J Mol Biol 1989 May 20
PMID:The DNA bending by acetylaminofluorene residues and by apurinic sites. 275 32

The structure of a dimer of the Escherichia coli catabolite gene activator protein has been refined at 2.5 A resolution to a crystallographic R-factor of 20.7% starting with coordinates fitted to the map at 2.9 A resolution. The two subunits are in different conformations and each contains one bound molecule of the allosteric activator, cyclic AMP. The amino-terminal domain is linked to the smaller carboxy-terminal domain by a nine-residue hinge region that exists in different conformations in the two subunits, giving rise to approximately a 30 degree rotation between the positions of the small domains relative to the larger domains. The amino-terminal domain contains an antiparallel beta-roll structure in which the interstrand hydrogen bonding is well-determined. The beta-roll can be described as a long antiparallel beta-ribbon that folds into a right-handed supercoil and forms part of the cyclic AMP binding site. Each cyclic AMP molecule is in an anti conformation and has ionic and hydrogen bond interactions with both subunits.
J Mol Biol 1987 Nov 20
PMID:Structure of a complex of catabolite gene activator protein and cyclic AMP refined at 2.5 A resolution. 282 39

An electrophoretic mobility shift assay was used to characterize interactions of nuclear proteins with a DNA segment in the enhancer element of the leukemogenic murine retrovirus SL3-3. Mutation of a DNA sequence of the 5'-TGTGG-3' type decreased transcription in vivo specifically in T-lymphocyte cell lines. Extracts of nuclei from different T-lymphocyte cell lines or cells from lymphoid organs resulted in much higher amounts of complexes in vitro with this DNA sequence than did extracts from other cell lines or organs tested. Differences were also found in the sets of complexes obtained with extracts from the different types of cells. The DNA sequence specificities of the different SL3-3 enhancer factor 1 (SEF1) protein complexes were found to be distinct from those of several other previously identified DNA motifs of the TGTGG type because of differences in several nucleotides critical for binding and because these other DNA motifs could not compete with the identified DNA sequence for binding of SEF1. Limited treatment with several different proteases cleaved the SEF1 proteins such that their DNA-binding domain(s) remained and created complexes with decreased and nondistinguishable electrophoretic mobility shifts and with new properties. These results indicate that the SEF1 proteins have a structure with a flexible and relatively vulnerable hinge region linking a DNA-binding domain(s) to a more variable domain(s) with other functions. We suggest that the binding of SEF1 is an essential factor for the T-cell tropism of SL3-3 and the ability of this virus to cause T-cell lymphomas.
Mol Cell Biol 1988 Apr
PMID:Differential protein binding in lymphocytes to a sequence in the enhancer of the mouse retrovirus SL3-3. 283 50

The avian erythroblastosis virus v-erbA locus potentiates the oncogenic transformation of erythroid and fibroblast cells and is derived from a host cell gene encoding a thyroid hormone receptor. We report here the use of site-directed mutagenesis to identify and characterize functional domains within the v-erbA protein. Genetic lesions introduced into a putative hinge region or at the extreme C-terminus of the v-erbA coding domain had no significant effect on the biological activity of this polypeptide. In contrast, mutations introduced within the cysteine-lysine-arginine-rich center of the v-erbA coding region, a DNA-binding domain in the thyroid and steroid hormone receptors, abolished or severely compromised the ability of the viral protein to function. Our results suggest that the mechanism of action of the v-erbA protein in establishing the neoplastic phenotype is closely related to its ability to interact with DNA, presumably thereby altering expression of host target genes by either mimicking or interfering with the action of the normal c-erbA gene product.
Mol Cell Biol 1988 Oct
PMID:Genetic dissection of functional domains within the avian erythroblastosis virus v-erbA oncogene. 284 34


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