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At least 1,315 records · Page 73Linked to original sources
PubMed1994

Alloantigenic recognition of artificial glycosyl phosphatidylinositol-anchored HLA-A2.1.

Alloantigen presentation by GPI-reanchored variants of the human class I MHC molecule HLA-A2.1 was studied in human cellular systems. To this end, we generated chimeric coding sequences for two GPI-modified HLA-A2.1 heavy chain derivatives. In these chimeras, the coding sequence for the HLA-A2.1 heavy chain was fused in-frame to alternative overlapping sequences from the 3'-end of human DAF containing the GPI-modification signal sequence. The encoded polypeptides HLA-A2.1:DAF-S and HLA-A2.1:DAF-L differed by 53 amino acids of additional DAF sequence in the latter. Both were detected on stably transfected C1R cell surfaces by HLA-A2.1-specific mAb, and their GPI-modification was confirmed by PI-PLC enzymatic cleavage. Immunoprecipitation analysis of surface-biotinylated C1R transfectants revealed heterodimeric association for both HLA-A2.1:DAF-L and HLA-A2.1:DAF-S heavy chains with beta 2m. Alloantigenic stimulation by, and cytotoxic recognition of, both HLA-A2.1:DAF-S/C1R and HLA-A2.1/CIR cells was observed; however, HLA-A2.1:DAF-L/C1R cells could not serve as allostimulators or allotargets. These findings establish that polymorphic human class I MHC molecules can function, when artificially GPI-reanchored, as alloantigenic targets. Moreover, the data suggest that the sequence bridging the HLA-A2 extracellular domain and the membrane can influence alloantigenic presentation.

Animals↗
PubMed1998

Vomeronasal/accessory olfactory system and pheromonal recognition.

Pregnancy block in mice requires exposure of recently mated females to urinary pheromones of a strange male, and when working with inbred strains this invariably requires urine from an outbred line. The pheromones which induce oestrus and early puberty in mice have been identified as the brevicomins and dihydrothiazoles. Since the same vomeronasal, neural and neuroendocrine pathways are also activated in pregnancy block, these compounds are likely candidates for pregnancy blocking pheromones. However, these relatively simple chemicals lack the capacity to code for differing mouse strains. Since large quantities of the polymorphic major urinary proteins from the lipocalin family found in urine serve as transporters for the dihydrothiazoles and brevicomins, and differ across strains, then these proteins must participate in pheromone recognition in the context of pregnancy block.

Animals↗
PubMed1988

Sequence and structure of the mouse gene coding for the largest neurofilament subunit.

We have determined the complete nucleotide sequence of the mouse gene encoding the neurofilament NF-H protein. The C-terminal domain of NF-H is very rich in charged amino acids (aa) and contains a 3-aa sequence, Lys-Ser-Pro, that is repeated 51 times within a stretch of 368 aa. The location of this serine-rich repeat in the phosphorylated domain of NF-H indicates that it represents the major protein kinase recognition site. The nfh gene shares two common intron positions with the nfl and nfm genes, but has an additional intron that occurs at a location equivalent to one of the introns in non-neuronal intermediate filament-coding genes. This additional nfh intron may have been acquired via duplication of a primordial intermediate filament gene.

Amino Acid Sequence↗
PubMed1999

Differential expression of allograft inflammatory factor 1 and of glutathione peroxidase during auto- and allograft response in marine sponges.

Very recently, Porifera (sponges) have been proven to be suitable model systems to study auto- and allograft recognition at the molecular level. Several potential immune molecules have been isolated from the marine sponges Suberites domuncula and Geodia cydonium, among them those which comprise Ig-like domains in their extracellular part. Here we report on the isolation of two cDNAs from S. domuncula that code for molecules involved in mammals in cytokine-mediated graft response; a putative allograft inflammatory factor 1 (AIF-1) and a non-selenium glutathione peroxidase (GPX). Both polypeptides share high similarity with the corresponding mammalian proteins. The expression of the two genes during auto- and allograft recognition in S. domuncula and G. cydonium was determined. It is shown that the expression of the AIF-1-related gene is upregulated only in allografts, while the GPX-related gene is expressed in the fusion zones formed between auto- as well as allografts. Taken together, these findings suggest that besides cell-mediated defense reactions a cytokine-dependent immune response is also elicited during graft recognition in sponges.

Amino Acid Sequence↗
PubMed1990

Isolation of a yeast gene, SRH1, that encodes a homologue of the 54K subunit of mammalian signal recognition particle.

A 1.7 kilobase HindIII fragment of Saccharomyces cerevisiae DNA was cloned by cross-hybridization with the Escherichia coli secY gene. The complete nucleotide sequence of the 2.6 kb fragment of the yeast genomic DNA containing the cross-hybridizing HindIII fragment was determined. The sequence showed no apparent similarity with that of the E. coli secY gene with the exception of a completely matched sequence of 21 bp, but it contained a 1,623 nucleotide open reading frame coding for a protein of 541 amino acids with a calculated Mr of 59,600. The N-terminal portion of 303 residues of the predicted sequence was homologous to the cytosolic domain of the alpha-subunit of the signal recognition particle receptor (SR alpha), including consensus sequence elements for a GTP binding site, whereas the C-terminal portion of 238 residues had an unusual methionine-rich domain containing several repetitive sequences. An mRNA of 2.0 kb was detected on Northern blotting analysis. The predicted sequence was 48% identical with the reported sequences of the 54K subunit of the mammalian signal recognition particle (SRP54) (Romisch K. et al. (1989) Nature 340, 478-483; Bernstein, H.D. et al. (1989) Nature 340, 482-486). We designated this gene as SRH1 (SRP54 homologue). Gene disruption experiments showed that the SRH1 gene product is essential for cell growth.

Amino Acid Sequence↗
PubMed2001

Odour-plume dynamics influence the brain's olfactory code.

The neural computations used to represent olfactory information in the brain have long been investigated. Recent studies in the insect antennal lobe suggest that precise temporal and/or spatial patterns of activity underlie the recognition and discrimination of different odours, and that these patterns may be strengthened by associative learning. It remains unknown, however, whether these activity patterns persist when odour intensity varies rapidly and unpredictably, as often occurs in nature. Here we show that with naturally intermittent odour stimulation, spike patterns recorded from moth antennal-lobe output neurons varied predictably with the fine-scale temporal dynamics and intensity of the odour. These data support the hypothesis that olfactory circuits compensate for contextual variations in the stimulus pattern with high temporal precision. The timing of output neuron activity is constantly modulated to reflect ongoing changes in stimulus intensity and dynamics that occur on a millisecond timescale.

Action Potentials↗
PubMed1990

Cytotoxic T lymphocyte recognition of the H-2-erbB hybrid gene product lacking the complete H-2 domain structure.

The chimeric mouse MHC class I gene derived from a recombinant H-2Kb gene, in which the coding region for a large part of alpha 1 and alpha 2 extracellular domains was replaced with a partial avian erythroblastosis virus erbB gene segment encoding the kinase domain, was successfully introduced into a mouse mastocytoma line P1.HTR (H-2d) and transcribed to mRNA. The transfectant cells expressed the chimeric gene product, which was reactive to a phosphotyrosine-specific antibody. When the chimeric gene transfectant was inoculated into CDF1(H-2d) or BDF1(H-2d/b) mice, it grew at an early time but regressed thereafter. Transfectant-specific as well as parental P1.HTR-specific antibody activities were demonstrated in the sera of these mice. Transfectant-specific cytotoxic T lymphocytes (CTL) were generated in the antigen-sensitized culture of spleen cells from the transfectant-immune mice. The CTL-mediated lysis of target chimeric gene transfectant cells was poorly inhibited by anti-H-2d antiserum, which blocked the lysis of parental P1.HTR cells by anti-tumor CTL developed in parallel. The former was, however, inhibited by either anti-transfectant antiserum or anti-phosphotyrosine antibody, which was ineffective for blocking the latter. Target cell lysis by either anti-transfectant or anti-tumor CTL was blocked by anti-CD8 monoclonal antibody but not by anti-CD4 antibody. It was suggested from these results that the H-2K-erbB hybrid gene product, which lacks complete three-domain class I structure, was recognized by CTL in a manner that was endogenous H-2 class I-independent but CD8-dependent.

Animals↗
PubMed1990

American Dental Association principles of ethics and code of professional conduct. With official advisory opinions revised to January 1990. Council on Ethics, Bylaws, and Judicial Affairs.

The ethical statements which have historically been subscribed to by the dental profession have had the benefit of the patient as their primary goal. Recognition of this goal, and of the education and training of a dentist, has resulted in society affording to the profession the privilege and obligation of self-government. The Association calls upon members of the profession to be caring and fair in their contact with patients. Although the structure of society may change, the overriding obligation of the dentist will always remain the duty to provide quality care in a competent and timely manner. All members must protect and preserve the high standards of oral health care provided to the public by the profession. They must strive to improve the care delivered--through education, training, research, and most of all, adherence to a stringent code of ethics, structured to meet the needs of the patient.

American Dental Association↗
PubMed1988

American Dental Association Principles of Ethics and Code of Professional Conduct. With official advisory opinions revised to July 1988. Council on Ethics, Bylaws, and Judicial Affairs.

The ethical statements which have historically been subscribed to by the dental profession have had the benefit of the patient as their primary goal. Recognition of this goal, and of the education and training of a dentist, has resulted in society affording to the profession the privilege and obligation of self-government. The Association calls upon members of the profession to be caring and fair in their contact with patients. Although the structure of society may change, the overriding obligation of the dentist will always remain the duty to provide quality care in a competent and timely manner. All members must protect and preserve the high standards of oral health care provided to the public by the profession. They must strive to improve the care delivered--through education, training, research and, most of all, adherence to a stringent code of ethics, structured to meet the needs of the patient.

American Dental Association↗
PubMed2003

Nucleotide shuffling and ssDNA recognition in Oxytricha nova telomere end-binding protein complexes.

Sequence-specific protein recognition of single-stranded nucleic acids is critical for many fundamental cellular processes, such as DNA replication, DNA repair, transcription, translation, recombination, apoptosis and telomere maintenance. To explore the mechanisms of sequence-specific ssDNA recognition, we determined the crystal structures of 10 different non-cognate ssDNAs complexed with the Oxytricha nova telomere end-binding protein (OnTEBP) and evaluated their corresponding binding affinities (PDB ID codes 1PH1-1PH9 and 1PHJ). The thermodynamic and structural effects of these sequence perturbations could not have been predicted based solely upon the cognate structure. OnTEBP accommodates non-cognate nucleotides by both subtle adjustments and surprisingly large structural rearrangements in the ssDNA. In two complexes containing ssDNA intermediates that occur during telomere extension by telomerase, entire nucleotides are expelled from the complex. Concurrently, the sequence register of the ssDNA shifts to re-establish a more cognate-like pattern. This phenomenon, termed nucleotide shuffling, may be of general importance in protein recognition of single-stranded nucleic acids. This set of structural and thermodynamic data highlights a fundamental difference between protein recognition of ssDNA versus dsDNA.

Animals↗
PubMed1994

Ribosome-messenger recognition in the absence of the Shine-Dalgarno interactions.

In an attempt to understand how Escherichia coli ribosomes recognize the initiator codon on mRNAs lacking the Shine-Dalgarno (SD) sequence, we have studied 30S initiation complex formation in extension inhibition (toeprinting) experiments using (-SD)mRNAs which are known to be reliably translated in E. coli: the plant viral messenger A1MV RNA 4 and two chimaeric mRNAs coding for beta-glucuronidase (GUS) and bearing the 5'-untranslated sequence of TMV RNA (omega) or the omega-derived sequence (CAA)n as 5'-leaders. Ribosomal protein S1 and IF3 have been found to be indispensable for translational initiation. Protein S1 appears to be a key recognition element. S1 binds to sequences within the leaders of (-SD)mRNAs thus providing their affinity to E. coli ribosomes.

Alfalfa mosaic virus↗
PubMed1987

The interaction of the recognition helix of lac repressor with lac operator.

We have constructed a system which allows systematic testing of repressor--operator interactions. The system consists of two plasmids. One of them carries a lac operon in which lac operator has been replaced by a unique restriction site into which synthetic operators can be cloned. The other plasmid carries the gene coding for the repressor, in our case a semisynthetic lacI gene of which parts can be exchanged in a cassette-like manner. A galE host allows us to select for mutants which express repressors with altered specificities. Here we report the change of specificity in the lac system by changing residues 1 and 2 of the recognition helix of lac repressor. The specificity changes are brought about cooperatively by the change of both residues. Exchanges of just one residue broaden the specificity. Our results hint that the recognition helix of lac repressor may possibly have the opposite orientation to those in Lambda cro protein or 434 CI repressor.

Amino Acid Sequence↗
PubMed2000

Purification and characterization of the DNA cleavage and recognition site of I-ScaI mitochondrial group I intron encoded endonuclease produced in Escherichia coli.

The second intron in the mitochondrial cytb gene of Saccharomyces capensis, belonging to group I, encodes a 280 amino acid protein containing two LAGLIDADG motifs. Genetic and molecular studies have previously shown that this protein has a dual function in the wild-type strain. It acts as a specific homing endonuclease I- Sca I promoting intron mobility and as a maturase promoting intron splicing. Here we describe the synthesis of a universal code equivalent to the mitochondrial sequence coding for this protein and the in vitro characterization of I- Sca I endonuclease activity, using a truncated mutant form of the protein p28bi2 produced in Escherichia coli. We have also determined the cleavage pattern as well as the recognition site of p28bi2. It was found that p28bi2 generates a double-strand cleavage downstream from the intron insertion site with 4 nt long 3'-overhangs. Mutational analysis of the DNA target site shows that p28bi2 recognizes a 16-19 bp sequence from positions -11 to +8 with respect to the intron insertion site.

Amino Acid Sequence↗
PubMed2002

Learning to discriminate simple sinusoidal gratings is task specific.

Learning transfer effects of a modified spatial frequency discrimination task with simple sinusoidal gratings on various untrained test tasks, testing performance in relative position, local width and global size discrimination, have been investigated. Six subjects were exposed to grating stimuli of varying spatial frequency and size but constant relative position while they had to respond only to spatial frequency. In the course of 7 consecutive days all subjects showed significant reduction of spatial frequency discrimination thresholds. Comparison of discrimination thresholds for the untrained test tasks, taken before and after the learning epoch, reveals complete learning transfer to spatial frequency discrimination with gratings of constant size and variable relative position, but complete lack of transfer when grating spatial frequency is shifted about one octave lower. Further, there is improvement of relative position discrimination and width discrimination of single luminance bars, which is not very specific for the learnt spatial frequency. Although size variation was part of the learning procedure, discrimination of global stimulus size did not improve. Generally, the observed scheme of learning transfer reveals that there is learning only for stimulus attributes that are behaviorally relevant in the learning task. The differential scheme of improvement and code usage in the test tasks strongly indicates involvement of higher stages capable of independent access to different coding domains, as well as attentionally guided attribute selection and suppression. Supported by other recent findings, it is suggested that discrimination learning can be understood as a higher level process of gradual refinement of code selection out of a rich code base provided by lower level stages.

Adult↗
PubMed1988

P300 and the word frequency effect.

In a lexical decision paradigm subjects viewed character strings and indicated if they were true words. Half of the stimulus words occur frequently and half occur infrequently in printed English. The probability that a stimulus was a true word varied across conditions. Event-related brain potentials (ERPs) and reaction time (RT) were recorded. The latency of the P300 ERP was used to estimate stimulus evaluation time independently of factors influenced by response selection and execution. Uncommon words were associated with longer P300 latencies, reduced P300 amplitude, and slower responses. The probability of a stimulus being a true word in any given sequence affected RT, but produced only small effects on P300 latency. The results suggest that: (1) the effects of word frequency originate early during processing, (2) stimulus probability affects response priming mostly for stimuli which do not evoke a high-level code, and (3) uncommon words require more processing capacity for their evaluation than common words. The results are discussed in the context of word recognition models.

Adult↗
PubMed1992

Artificial immunoglobulin G-binding protein mimetic to staphylococcal protein A. Its production and application to affinity purification of immunoglobulin G.

Staphylococcal protein A consists of a single polypeptide with five immunoglobulin G (IgG)-binding domains, which are linked as E-D-A-B-C in this order from the amino terminal. The DNA coding domains A-B were polymerized one to six times linearly, taking advantage of the non-palindromic nucleotide sequence of the AccI recognition site and the resultant DNAs were inserted in pTRP vector carrying trp promoter. The artificial IgG-binding proteins [pA(AB)1-6], which had been expressed in Escherichia coli JM109, were purified by methods involving IgG-Sepharose affinity chromatography. Among pA(AB)1-6 immobilized on cyanogen bromide-Sepharose, pA(AB)4-Sepharose was the highest in IgG-binding capacity at the same level of mg protein per ml gel, about 30% higher than protein A-Sepharose. At 8 mg protein per ml gel, it bound and eluted about 24 mg of IgG from rabbit serum. Its IgG-binding capacities were the highest with porcine, rabbit, human and guinea pig sera, intermediate with bovine, horse and sheep sera and the lowest with mouse, goat, rat and chicken sera.

Amino Acid Sequence↗