Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A peptide analogue of [8-arginine]vasopressin (AVP) with Lys substituted for Gly at position 9 ([d(CH2)5Tyr(Me)2LysNH2(9)]AVP; ALVP) has been synthesized as a precursor for the production of heterofunctional vasopressin receptor ligands. Three heterofunctional ligands have been prepared by attaching biotin and a photoreactive cross-linker capable of iodination, either alone or in combination, to the epsilon-amino group of Lys at position 9 in ALVP. The binding characteristics of these novel ligands have been determined at the V1a and V2 vasopressin receptors by employing membrane preparations of rat liver and kidney respectively. All of the analogues synthesized during the course of this study bound selectively, and with high affinity, to the V1a vasopressin receptor subtype. Our results demonstrate that the strategies described in this paper provide a convenient means of synthesizing heterofunctional vasopressin receptor ligands with preservation of subtype-specific, high affinity binding characteristics. These parameters establish the potential value of the analogues as probes for investigating V1a receptor structure and function.
J Mol Endocrinol 1992 Oct
PMID:Design and synthesis of heterofunctional V1a-selective vasopressin receptor ligands with lysine at position 9. 141 83

The dependence of amino acid frequency on sequence length has been examined for the 20 natural amino acids using a set of 2275 protein sequences with little sequence identity. As expected, the frequency of cysteine increases dramatically for sequences shorter than 100 amino acids with a length-dependence that corresponds to an average of two Cys per sequence independent of length. Surprisingly dramatic changes were also observed for the frequencies of arginine, lysine, aspartic acid, and glutamic acid: Arg and Lys frequencies increase for short sequences whereas Asp and Glu frequencies decrease. These changes do not appear to be due to an over-abundance of DNA- and membrane-binding proteins in the database and may, therefore, be related to protein stability. Possible stabilizing mechanisms include increased hydrogen bonding by Arg and increased hydrophobic stabilization due to the amphiphilic character of Arg and Lys. These observations suggest that amino acid composition played an important role in the evolution of small proteins.
J Mol Biol 1992 Oct 20
PMID:Amino acid preferences of small proteins. Implications for protein stability and evolution. 143 4

At least 3 structural protein precursors of the eggshell are synthesized and stockpiled in the extensive vitelline cells of the liver fluke Fasciola hepatica L. One of these, vitelline protein B, consists of a closely related family of proteins that owes its apparent electrophoretic heterogeneity to variations in the Tyr to DOPA conversion as well as to subtle variations in the primary sequence. The efficiency of the Tyr to DOPA conversion ranges from a maximum of about 90% to a minimum of 55% in the protein. Trypsin digestion in borate buffer at pH 8 was used to produce DOPA-peptides for sequencing. Notably, trypsin does not cleave Arg/Lys-DOPA sequences at borate concentrations greater than 0.15 M. Peptides with DOPA-containing sequences most frequently have flanking amino acids such as Lys, Ser, or Asp on the N-terminal side and Gly or Asp on the C-terminal side. All protein variants fall within a narrow molecular weight range (30-33 kDa), a pI range of 6.9 to 8.3, and the collective majority would appear to share a common N-terminal sequence up to residue 28. The results suggest some combination of the following: variations in post-translational hydroxylation, alternative post-transcriptional splicing and/or the existence of multiple gene copies of eggshell precursors. The latter have been shown to occur in the blood fluke Schistosoma mansoni [15].
Mol Biochem Parasitol 1992 Sep
PMID:Eggshell precursor proteins of Fasciola hepatica, II. Microheterogeneity in vitelline protein B. 143 55

In order to demonstrate that the nucleic acid-binding activities of vimentin are dictated by its Arg-rich N-terminal head domain, this was cut off at position Lys96 with lysine-specific endoproteinase and analysed for its capacity to associate with a variety of synthetic and naturally occurring nucleic acids. The isolated polypeptide (vim NT) showed a preference for single-stranded (ss) polynucleotides, particularly for ssDNAs of high G-content. A comparison of the sequence and predicted secondary structure of vim NT with that of two prokaryotic ssDNA-binding proteins, G5P and G32P of bacteriophages fd and T4, respectively, revealed that the nucleic acid-binding region of all three polypeptides is almost entirely in the beta-conformation and characterized by a very similar distribution of aromatic amino acid residues. A partial sequence of vim NT can be folded into the same beta-loop structure as the DNA-binding wing of G5P of bacteriophage fd and related viruses. As in the case of G5P, nitration of the Tyr residues with tetranitromethane was blocked by single-stranded nucleic acids. This and spectroscopic data indicate intercalation of the Tyr aromatic ring systems between the bases of the nucleic acids and thus the contribution of a stacking component to the binding reaction. The binding was accompanied by significant changes in the ultraviolet absorption spectra of both vim NT and single-stranded nucleic acids. Upon mixing of vim NT with nucleic acids, massive precipitation of the reactants occurred, followed by the quick rearrangement of the aggregates with the formation of specific and soluble association products. Even at very high ionic strengths, at which no electrostatic reaction should be expected, a distinct fraction of vim NT incorporated naturally occurring ssRNAs and ssDNAs into fast sedimenting complexes, suggesting co-operative interaction of the polypeptide with the nucleic acids. In electron microscopy, the complexes obtained from 28 S rRNA appeared as networks of extended nucleic acid strands densely covered with vim NT, in contrast to the compact random coils of uncomplexed RNA. The networks produced from fd DNA were heterogeneous in appearance and their nucleoprotein strands in rare cases were very similar to the rod-like structures of G5P-fd DNA complexes.
J Mol Biol 1992 Nov 05
PMID:Characterization of the nucleic acid-binding activities of the isolated amino-terminal head domain of the intermediate filament protein vimentin reveals its close relationship to the DNA-binding regions of some prokaryotic single-stranded DNA-binding proteins. 144 93

The tripeptide serine-lysine-leucine (SKL) occurs at the carboxyl terminus of many peroxisomal proteins and serves as a peroxisomal targeting signal. Saccharomyces cerevisiae has two isozymes of citrate synthase. The peroxisomal form, encoded by CIT2, terminates in SKL, while the mitochondrial form, encoded by CIT1, begins with an amino-terminal mitochondrial signal sequence and ends in SKN. We analyzed the importance of SKL as a topogenic signal for citrate synthase, using oleate to induce peroxisomes and density gradients to fractionate organelles. Our experiments revealed that SKL was necessary for directing citrate synthase to peroxisomes. C-terminal SKL was also sufficient to target a leaderless version of mitochondrial citrate synthase to peroxisomes. Deleting this tripeptide from the CIT2 protein caused peroxisomal citrate synthase to be missorted to mitochondria. These experiments suggest that the CIT2 protein contains a cryptic mitochondrial targeting signal.
Mol Cell Biol 1992 Dec
PMID:Alternative topogenic signals in peroxisomal citrate synthase of Saccharomyces cerevisiae. 144 89

A variety of techniques, including filter binding, footprinting, and gel retardation, can be used to assay the transcriptional activator GAL4 (Gal4p) through the initial steps of its purification from yeast cells. Following DNA affinity chromatography, Gal4p still bound DNA selectively when assayed by filter binding or footprinting. However, the affinity-purified protein was no longer capable of forming a stable complex with DNA, as assayed by gel retardation. Mixing the purified Gal4p with the flowthrough fraction from the DNA affinity column restored gel retardation complex formation. Gel retardation assays were used to monitor the purification of a heat-stable Gal4p-DNA complex stabilization activity from the affinity column flowthrough. The activity coeluted from the final purification step with polypeptides of 21 and 27 kDa. The yeast gene encoding the 21-kDa protein was cloned on the basis of its N-terminal amino acid sequence. The gene, named EGD1 (enhancer of GAL4 DNA binding), encodes a highly basic protein (21% lysine and arginine) with a predicted molecular mass of 16.5 kDa. The amino acid sequence of the EGD1 product, Egd1p, is highly similar to that of the human protein BTF3 (X. M. Zheng, D. Black, P. Chambon, and J. M. Egly, Nature [London] 344:556-559, 1990). Although an egd1 null mutant was viable and Gal+, induction of the galactose-regulated genes in the egd1 mutant strain was significantly reduced when cells were shifted from glucose to galactose.
Mol Cell Biol 1992 Dec
PMID:The EGD1 product, a yeast homolog of human BTF3, may be involved in GAL4 DNA binding. 144 98

A second-site mutation that restored DNA binding to ADR1 mutants altered at different positions in the two zinc fingers was identified. This mutation (called IS1) was a conservative change of arginine 91 to lysine in a region amino terminal to the two zinc fingers and known from previous experiments to be necessary for DNA binding. IS1 increased binding to the UAS1 sequence two- to sevenfold for various ADR1 mutants and twofold for wild-type ADR1. The change of arginine 91 to glycine decreased binding twofold, suggesting that this arginine is involved in DNA binding in the wild-type protein. The increase in binding by IS1 did not involve protein-protein interactions between the two ADR1 monomers, nor did it require the presence of the sequences flanking UAS1. However, the effect of IS1 was influenced by the sequence of the first finger, suggesting that interactions between the region amino terminal to the fingers and the fingers themselves could exist. A model for the role of the amino-terminal region based on these results and sequence homologies with other DNA-binding motifs is proposed.
Mol Cell Biol 1992 Dec
PMID:A mutation outside the two zinc fingers of ADR1 can suppress defects in either finger. 144 3

The crystal structure of subtilisin BL, an alkaline protease from Bacillus lentus with activity at pH 11, has been determined to 1.4 A resolution. The structure was solved by molecular replacement starting with the 2.1 A structure of subtilisin BPN' followed by molecular dynamics refinement using X-PLOR. A final crystallographic R-factor of 19% overall was obtained. The enzyme possesses stability at high pH, which is a result of the high pI of the protein. Almost all of the acidic side-chains are involved in some type of electrostatic interaction (ion pairs, calcium binding, etc.). Furthermore, three of seven tyrosine residues have potential partners for forming salt bridges. All of the potential partners are arginine with a pK around 12. Lysine would not function well in a salt bridge with tyrosine as it deprotonates at around the same pH as tyrosine ionizes. Stability at high pH is acquired in part from the pI of the protein, but also from the formation of salt bridges (which would affect the pI). The overall structure of the enzyme is very similar to other subtilisins and shows that the subtilisin fold is more highly conserved than would be expected from the differences in amino acid sequence. The amino acid side-chains in the hydrophobic core are not conserved, though the inter-residue interactions are. Finally, one third of the serine side-chains in the protein have multiple conformations. This presents an opportunity to correlate computer simulations with observed occupancies in the crystal structure.
J Mol Biol 1992 Nov 20
PMID:The crystal structure of the Bacillus lentus alkaline protease, subtilisin BL, at 1.4 A resolution. 145 65

In a protein antigen the number of epitopes that are presented by the MHC molecules to the T cells is generally limited. This phenomenon of immunodominance determines the T cell response to a given antigen. To understand the molecular basis of epitope selection we have analysed the hierarchy of T cell epitopes in a repeating synthetic polypeptide antigen Poly 18, Poly EYK(EYA)5 in the mice of H-2d haplotype. Because of its repeating nature, all the potential epitopes of Poly EYK(EYA)5 generated as a result of antigen processing will have extensive sequence overlap, therefore, providing an excellent system to investigate the molecular basis of T cell peptide epitope selection in vivo. We have synthesized a series of 12 and 15 amino acid peptides to mimic these epitopes. In H-2d mice Poly EYK(EYA)5 elicits T cell clones that optimally react with 15 amino acid peptides EYK(EYA)4 and/or (EYA)5. Similar results were obtained when related 12 amino acid peptides EYK(EYA)3 and/or (EYA)4 are used. (EYA)5 reactive T cell clones appear to be very heterogenous and much larger in number than EYK(EYA)4 reactive clones. (EYA)5 reactive clones could be elicited by at least three short Poly-18 derived epitopes (EYA)4, EYK(EYA)3 and (EYA)3EYK while EYK(EYA)4 reactive clones elicited only by the EYK(EYA)3 epitope. However, we observed the dominance of (EYA)5 reactive clones even when EYK(EYA)3 was used as an immunogen and this could be related to the degeneracy of their antigen specificity. Our earlier antigen competition studies suggest that (EYA)5 does not compete with EYK(EYA)4 epitope in binding to I-Ad. Therefore, there is no intramolecular competition between these epitopes to activate T cells. The epitope (EYA)3EYK appears to be subdominant since it can elicit Poly EYK(EYA)5 specific T cells upon immunization but does not appear to be part of Poly EYK(EYA)5 repertoire. Peptides such as (EYA)2EYKEYA or EYAEYK(EYA)2 with lysine substitution in the middle of the sequence were non immunogeneic. Similar results were obtained when the larger 15 amino acid peptides were used as antigen. Another level of epitope immunodominance is seen when substituted peptides of the two immunodominant epitopes are used. Some of these epitopes have potential to be part of the Poly 18 repertoire but they are greatly under represented when intact Poly 18 is used as antigen. The unusual hierarchy observed for immunodominance in these overlapping epitopes of EYK(EYA)5 sequence suggest a bias in the selection of T cell repertoire based upon the crossreactivity between potential epitopes generated as a result of antigen processing.
Mol Immunol 1992 Dec
PMID:Evidence for immunodominance between closely related epitopes in the selection of T cell repertoire: hierarchy of T cell epitopes in a repeating sequence. 145 65

We have isolated a rab-related (responsive to ABA) gene, rab18 from Arabidopsis thaliana. The gene encodes a hydrophilic, glycine-rich protein (18.5 kDa), which contains the conserved serine- and lysine-rich domains characteristic of similar RAB proteins in other plant species. The rab18 mRNA accumulates in plants exposed to low temperature, water stress or exogenous ABA but not in plants subjected to heat shock. This stress-related accumulation of the rab18 mRNA is markedly decreased in the ABA-synthesis mutant aba-1, the ABA-response mutant abi-1 or in wild-type plants treated with the carotenoid synthesis inhibitor, fluridone. Exogenous ABA treatment can induce the rab18 mRNA in the aba-1 mutant but not in the abi-1 mutant. These results provide direct genetic evidence for the ABA-dependent regulation of the rab18 gene in A. thaliana.
Plant Mol Biol 1992 Dec
PMID:The expression of a rab-related gene, rab18, is induced by abscisic acid during the cold acclimation process of Arabidopsis thaliana (L.) Heynh. 844 52


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