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K Chater

Publications and source records attributed to K Chater.

17 recordsLinked to original sources
PubMed2002

The GlnD and GlnK homologues of Streptomyces coelicolor A3(2) are functionally dissimilar to their nitrogen regulatory system counterparts from enteric bacteria.

Glutamine synthetase I (GSI) enzyme activity in Streptomyces coelicolor is controlled post-translationally by the adenylyltransferase (GlnE) as in enteric bacteria. Although other homologues of the Escherichia coli Ntr system (glnK, coding for a PII family protein; and glnD, coding for an uridylyltransferase) are found in the S. coelicolor genome, the regulation of the GSI activity was found to be different. The functions of glnK and glnD were analysed by specific mutants. Surprisingly, biochemical assay and two-dimensional PAGE analysis showed that modification of GSI by GlnE occurs normally in all mutant strains, and neither GlnK nor GlnD are required for the regulation of GlnE in response to nitrogen stimuli. Analysis of the post-translational regulation of GlnK in vivo by two-dimensional PAGE and mass spectrometry indicated that it is subject to both a reversible and a non-reversible modification in a direct response to nitrogen availability. The irreversible modification was identified as removal of the first three N-terminal amino acid residues of the protein, and the reversible modification as adenylylation of the conserved tyro-sine 51 residue that is known to be uridylylated in E. coli. The glnD insertion mutant expressing only the N-terminal half of GlnD was capable of adenylylating GlnK, but was unable to perform the reverse deadenylylation reaction in response to excess ammonium. The glnD null mutant completely lacked the ability to adenylylate GlnK. This work provides the first example of a PII protein that is modified by adenylylation, and demonstrates that this reaction is performed by a homologue of GlnD, previously described only as a uridylyltransferase enzyme.

Amino Acid Sequence↗
PubMed1999

Risk and representation: older people and noncompliance.

In this paper it is argued that the way in which ageing is portrayed is culturally constructed and historically located. The terminology used to describe older people becomes part of nursing taxonomy but the issue that it is a cultural construct remains hidden. Nurses use histories and records as a means of communication about the condition of the client or patient. The notes mediate the way in which the patient comes to be known as an individual in need of services and help define the way in which nursing care is undertaken. Nursing notes help construct the 'manageable' patient. Noncompliance disrupts this notion of the manageable patient and it challenges medical and nursing dominance of the body. However, noncompliance then becomes reinterpreted as 'risk', which has the effect of extending the clinical gaze from the confines of the body to extra-corporeal spaces. Older people, because of their corporeality, can subvert and resist this clinical gaze.

Aged↗
PubMed1999

David Hopwood and the emergence of Streptomyces genetics.

Streptomyces spp. are unusual among bacteria in growing as mycelial colonies with sporulating aerial hyphae. They are very important as the source of most of the major antibiotics. Pioneering work by David Hopwood in the 1950s and 1960s established Streptomyces coelicolor A3(2) as the model system for the genus. Since then he has led successive key phases of research on this organism. In the 1970s, plasmids were discovered and characterised, and used both to establish conditions for transformation and in the subsequent development of cloning vectors. Protoplasts were exploited in both transformation and highly efficient cell fusion. In the 1980s, the early cloning of resistance genes from antibiotic-producing strains was followed by the cloning of antibiotic biosynthetic gene clusters, and the development of general methods and probes for the cloning of such clusters from diverse species. Analysis of these gene sets led to wide-ranging inferences about the biosynthesis of the important polyketide class of antibiotics, and to the production of hybrid antibiotics, and then, in the last decade, to more sophisticated combinatorial biosynthesis of designer molecules. In parallel, David Hopwood's work has also provided a crucial platform for studies of the regulation of the morphological and physiological differentiation that is manifested by sporulating antibiotic-producing colonies. Most recently, his involvement in the physical mapping of the entire 8 Mb genome of S. coelicolor A3(2) has culminated in its complete DNA sequencing: a project that should be completed under his management during the year 2000.

Anti-Bacterial Agents↗
PubMed1998

The bldD gene of Streptomyces coelicolor A3(2): a regulatory gene involved in morphogenesis and antibiotic production.

The bld mutants of Streptomyces coelicolor A3(2) are blocked at the earliest stage of sporulation, the formation of aerial hyphae, and are pleiotropically defective in antibiotic production. Using a phage library of wild-type S. coelicolor DNA, we isolated a recombinant phage which restored both sporulation and antibiotic production to strains carrying the single known bldD mutation. Nucleotide sequence analysis of a 1.3-kb complementing subclone identified an open reading frame, designated bldD, encoding a translation product of 167 amino acid residues. Nucleotide sequence analysis of the bldD-containing fragment amplified from the chromosome of a bldD mutant strain revealed a point mutation changing a tyrosine residue at amino acid position 62 to a cysteine. Although a comparison of the BldD sequence to known proteins in the databases failed to show any strong similarities, analysis of the BldD sequence for secondary structural elements did reveal a putative helix-turn-helix, DNA recognition element near the C terminus of the protein. A comparison of bldD transcript levels in the bldD+ and bldD mutant strains using both Northern blot analysis and S1 nuclease protection studies showed vast overexpression of bldD transcripts in the mutant, suggesting that BldD negatively regulates its own synthesis. High-resolution S1 nuclease mapping identified the transcription start point as a G residue 63 nucleotides upstream from the bldD start codon and 7 nucleotides downstream from -10 and -35 sequences resembling E. coli-like streptomycete promoters.

Amino Acid Sequence↗
PubMed1997

Carbonic anhydrase II (CA II) deficiency in Maghrebian patients: evidence for founder effect and genomic recombination at the CA II locus.

A splice junction mutation at the exon 2-intron 2 boundary of the carbonic anhydrase II (CA II) gene was previously shown to be the unique mutation underlying the CA II deficiency syndrome in patients of Arab descent. Fourteen Tunisian (Maghrebian) families with a history of osteopetrosis, renal tubular acidosis, mental retardation, and CA II deficiency were studied to test the hypothesis that the mutation, found in all 24 patients, derived from a common ancestor originating in the Arabic Peninsula. A filiation study permitted us to trace these families back to a common Arabic tribe that settled in the Maghreb in the tenth century, indicating a common ethnic origin for these families. Segregation of the mutation with a TaqI biallelic restriction site polymorphism upstream of the CA II gene was studied by sequence-tagged site analysis in all the family members. These studies showed cosegregation of the Taq (-) allele with the mutation in 12 families out of 14. This observation supports a founder effect to explain the common CA II deficiency allele in this population. In the remaining two families, a genomic recombination or gene conversion occurred between the TaqI restriction marker and the mutation causing the disease. The relatively high recombination frequency suggests the presence of a hot spot for recombination or gene conversion at the CA II locus.

Acidosis, Renal Tubular↗
PubMed1997

Culture, multiculturalism and ageing: towards a postmodern interpretation.

Nursing care of older people is informed by many different theoretical frameworks. This paper contends that two such frameworks, the lifecourse theory and some aspects of Western medicine are cultural constructs that are often seen as normative therefore obscuring the power relations implicit in these constructions. The paper argues that nurses are implicated in reproducing these cultural constructions but more particularly, these constructions may have no meaning for non-English speaking older people. Finally, the paper suggests that nurses could benefit from a more localised, contextual view of ageing.

Aged↗
PubMed1996

Dilemmas of difference and the politics of comparison: cross-cultural research on dementia.

This paper examines some of the theoretical and methodological issues that were raised when I undertook cross-cultural research on dementia. The main concern addressed in this paper is the difficulty of representation within cultural groups. The paper contends that whilst representation can lead to perceived homogenization of a group, thus blurring intragroup differences, it is at times expedient to use this method in order to further the cause of that group. This paper proposes a way of presenting findings that, whilst meeting the aims of the research, compromises neither the participants nor the researcher. This paper also represents part of the decision trail the author left while carrying out the research.

Cross-Cultural Comparison↗
PubMed1995

Alarms and diversions: the biochemistry of development.

In considering biochemical aspects of development over a range of different organisms--plants, animals, fungi and bacteria--some ubiquitous themes emerge. Many of the regulatory mechanisms being discovered in higher organisms have already been found in yeast, and there are examples of similar mechanisms in bacteria, notably, analogies and even homologies in multistep cascades involving phosphorylation and negatively acting steps; interplay between development and the cell cycle; and emerging evidence that metabolic pathways can be important developmental agents. On the other hand, those topics that remain resolutely organism-specific may serve as a warning to those who tend to overgeneralize, or as the nucleus for the next generation of general insights.

Animals↗
PubMed1990

The Streptomyces coelicolor A3(2) bldB region contains at least two genes involved in morphological development.

Streptomyces coelicolor A3(2) bldB mutants are blocked in the formation of aerial hyphae. A phage library of wild-type S. coelicolor DNA was used to isolate recombinant phages which restore wild-type morphological development to several bldB mutants. Of several mutations, one, bld-28, previously mapped at bldB was not complemented by the cloned region, indicating that the bldB locus is composed of at least two distinct genes. Partial localization of bldB-complementing activity showed that a 1.5 kb fragment is sufficient for complementation of the bld-15 mutation whereas bld-17 requires the same region as well as additional sequences. Under stringent conditions, genomic DNA hybridizing to the cloned sequences was absent from other Streptomyces species, including the closely related Streptomyces lividans 66. DNA sequences causing marked plasmid structural instability in S. coelicolor, but not in S. lividans, are also located in this region.

DNA, Bacterial↗
PubMed1988

Visualizing gene expression in time and space in the filamentous bacterium Streptomyces coelicolor.

Streptomycetes are prokaryotic microorganisms that exhibit a complex, mycelial fungus-like cycle of morphological differentiation. Development involves at least two spatially separated types of cells: the branching hyphae of the substrate mycelium, which penetrate the stratum upon which the colony feeds, and the upwardly protruding hyphae of the aerial mycelium, which undergo metamorphosis into spores. The luciferase-encoding luxA and luxB operon of the luminescent marine bacterium Vibrio harveyi was used as a promoter probe to visualize gene expression in differentiating colonies of Streptomyces coelicolor. Promoters for developmental genes of several kinds gave distinctive temporal and spatial patterns of light emission.

DNA, Bacterial↗
PubMed1983

Nonpharmacologic intervention in acute alcohol withdrawal.

The importance of nonpharmacologic and pharmacologic interventions in the treatment of alcohol withdrawal is not known. A randomized, double-blind, placebo-controlled trial was conducted with 41 patients in alcohol withdrawal in an emergency department. The patients received either supportive care (10 min of standardized assessments, reassurance, reality orientation, and nursing care an hour) with three doses of sublingual lorazepam 2 mg every 2 hr (21 patients, drug group) or supportive care with three doses of sublingual placebo every 2 hr (20 patients, no-drug group). Immediately before each drug dose, the clinical course of alcohol withdrawal was assessed hourly by the Clinical Institute Withdrawal Assessment for Alcohol (CIWA-A). Interraters reliability in using CIWA-A was high. After each assessment, supportive care was given for 10 min before each dose. After completion of a 7-hr initial phase, patients were discharged and reassessed daily for 5 days. Thirty-seven patients (90.2%) improved in the initial phase. Treatment failures (CIWA-A greater than 10) were more common in the patients treated without drug (3/20, 15%) than in those treated with drug (1/21, 4.8%). Overall variations in intergroup CIWA-A scores during the initial phase were not significant. The rate of improvement of CIWA-A scores over the first 2 hr after drug was slightly faster in patients receiving lorazepam than in the control group. CIWA-A scores were the same during follow-up. These results indicate that most outpatients in mild to moderate alcohol withdrawal without medical complications improve without drug therapy in the emergency department setting.

Adult↗