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M Potts

Publications and source records attributed to M Potts.

At least 37 records · Page 2Linked to original sources
PubMed2000

Active Fe-containing superoxide dismutase and abundant sodF mRNA in Nostoc commune (Cyanobacteria) after years of desiccation.

Active Fe-superoxide dismutase (SodF) was the third most abundant soluble protein in cells of Nostoc commune CHEN/1986 after prolonged (13 years) storage in the desiccated state. Upon rehydration, Fe-containing superoxide disumutase (Fe-SOD) was released and the activity was distributed between rehydrating cells and the extracellular fluid. The 21-kDa Fe-SOD polypeptide was purified, the N terminus was sequenced, and the data were used to isolate sodF from the clonal isolate N. commune DRH1. sodF encodes an open reading frame of 200 codons and is expressed as a monocistronic transcript (of approximately 750 bases) from a region of the genome which includes genes involved in nucleic acid synthesis and repair, including dipyrimidine photolyase (phr) and cytidylate monophosphate kinase (panC). sodF mRNA was abundant and stable in cells after long-term desiccation. Upon rehydration of desiccated cells, there was a turnover of sodF mRNA within 15 min and then a rise in the mRNA pool to control levels (quantity of sodF mRNA in cells in late logarithmic phase of growth) over approximately 24 h. The extensive extracellular polysaccharide (glycan) of N. commune DRH1 generated superoxide radicals upon exposure to UV-A or -B irradiation, and these were scavenged by SOD. Despite demonstrated roles for the glycan in the desiccation tolerance of N. commune, it may in fact be a significant source of damaging free radicals in vivo. It is proposed that the high levels of SodF in N. commune, and release of the enzyme from dried cells upon rehydration, counter the effects of oxidative stress imposed by multiple cycles of desiccation and rehydration during UV-A or -B irradiation in situ.

Amino Acid Sequence↗
PubMed2000

Structural characterization of the released polysaccharide of desiccation-tolerant Nostoc commune DRH-1.

The structure of the viscous extracellular polysaccharide (glycan) of desiccation-tolerant Nostoc commune DRH-1 was determined through chromatographic and spectroscopic methods. The polysaccharide is novel in that it possesses a 1-4-linked xylogalactoglucan backbone with D-ribofuranose and 3-O-[(R)-1-carboxyethyl]-D-glucuronic acid (nosturonic acid) pendant groups. The presence of D-ribose and nosturonic acid as peripheral groups is unusual, and their potential roles in modulating the rheological properties of the glycan are discussed. Nosturonic acid was present in the glycans of N. commune from diverse geographic locations, suggesting that this uronic acid is an integral component of this cosmopolitan anhydrophile.

Carbohydrate Conformation↗
PubMed2000

Thinking about vaginal microbicide testing.

A vaginal microbicide could slow the spread of HIV. To date, volunteers in placebo-controlled trials of candidate microbicides have been counseled to use condoms. This does not reduce the number of volunteers exposed to possible risk, but it shifts the allotment of risk from those conducting the trial to those women who may be least able to make autonomous decisions. Alternative ways of meeting the obligation to offer volunteers active benefits are explored. Counseling the use of condoms prolongs clinical trials and could cause tens of thousands of otherwise avoidable deaths.

Administration, Intravaginal↗
PubMed1999

Life among the primitives: protein O-phosphatases in prokaryotes.

Prokaryotes contain at least five distinct families of protein O-phosphatases, including AceK, the chimeric isocitrate dehydrogenase kinase/phosphatase, and four protein phosphatase families first identified and characterized in Eukaryotes. The latter consist of the PPP and PPM families of protein-serine/threonine phosphatases, and the low molecular weight and conventional families of protein-tyrosine phosphatases. Prokaryotic protein O-phosphatases participate in the regulation of metabolic processes and the transduction of environmental signals. Certain pathogenic bacteria employ protein-tyrosine phosphatases as virulence factors, injecting them into host cells where they enzymatically perturb the phosphorylation state of proteins therein. While our understanding of protein O-phosphorylation events in Prokaryotes only now is emerging from its infancy, their phylogenetic diversity and malleability to genetic manipulation render these "simple'" organisms powerful vehicles for answering fundamental questions concerning the origins and evolution of this key biological regulatory mechanism.

Phosphoprotein Phosphatases↗
PubMed1999

A cyanobacterial hemoglobin with unusual ligand binding kinetics and stability properties.

The glbN gene of the cyanobacterium Nostoc commune UTEX 584 encodes a hemoprotein, named cyanoglobin, that has high oxygen affinity. The basis for the high oxygen affinity of cyanoglobin was investigated through kinetic studies that utilized stopped-flow spectrophotometry and flash photolysis. Association and dissociation rate constants were measured at 20 degrees C for oxygen, carbon monoxide, nitric oxide, and methyl and ethyl isocyanides. The association rate constants for the binding of these five ligands to cyanoglobin are the highest reported for any naturally occurring hemoglobin, suggesting an unhindered and apolar ligand binding pocket. Cyanoglobin also shows high rates of autoxidation and hemin loss, indicating that the prosthetic group is readily accessible to solvent. The ligand binding behavior of cyanoglobin was more similar to that of leghemoglobin a than to that of sperm whale myoglobin. Collectively, the data support the model of cyanoglobin function described by Hill et al. [(1996) J. Bacteriol. 178, 6587-6598], in which cyanoglobin sequesters oxygen, and presents it to, or is a part of, a terminal cytochrome oxidase complex in Nostoc commune UTEX 584 under microaerobic conditions, when nitrogen fixation, and thus ATP demand, is maximal.

Bacterial Proteins↗
PubMed1999

Making Cairo work.

The 1994 International Conference on Population and Development set broad new goals for family planning and reproductive health. The resources available to fund these much needed programmes, however, are much smaller than was originally calculated. To divide the limited budgets for the maximum health impact, likely resource flows need to be set against the cost of various family planning and reproductive health interventions. Preliminary analysis suggests that selection of cost-effective delivery of family planning services would still meet much of the need for family planning, and that some progress could be made towards improved control of sexually transmitted diseases.

Congresses as Topic↗
PubMed1999

International aspects of ethical problems in obstetrics and gynaecology.

Until the middle of the twentieth century, family planning was commonly condemned as an immoral enterprise. This chapter argues that ethical disapproval made access to fertility regulation difficult, and that while the rich and educated were often able to access the services they needed, typically the poor could not. Thus, ethical interpretations caused much of the differential fertility observed between social classes, ethnic groups and ultimately much of the explosion in population that has characterized the last 50 years. Since the 1960s human rights have been interpreted to encompass the right to decide the number and spacing of children and as a result access to contraception has improved. Where several methods of contraception (backed up by safe abortion) are available, fertility always falls. But, unfortunately, consensus has not been reached on how to specify particular sets of rights (e.g. decision-making for adolescents), and no consensus exists on how to balance the opposing rights of the mother and fetus in the case of abortion. The ethics of the one-child family in China is also noted.

Abortion, Legal↗
PubMed1998

The serine, threonine, and/or tyrosine-specific protein kinases and protein phosphatases of prokaryotic organisms: a family portrait.

Inspection of the genomes for the bacteria Bacillus subtilis 168, Borrelia burgdorferi B31, Escherichia coli K-12, Haemophilus influenzae KW20, Helicobacter pylori 26695, Mycoplasma genitalium G-37, and Synechocystis sp PCC 6803 and for the archaeons Archaeoglobus fulgidus VC-16 DSM4304, Methanobacterium thermoautotrophicum delta H, and Methanococcus jannaschii DSM2661 revealed that each contains at least one ORF whose predicted product displays sequence features characteristic of eukaryote-like protein-serine/threonine/tyrosine kinases and protein-serine/threonine/tyrosine phosphatases. Orthologs for all four major protein phosphatase families (PPP, PPM, conventional PTP, and low molecular weight PTP) were present in the bacteria surveyed, but not all strains contained all types. The three archaeons surveyed lacked recognizable homologs of the PPM family of eukaryotic protein-serine/threonine phosphatases; and only two prokaryotes were found to contain ORFs for potential phosphatases from all four major families. Intriguingly, our searches revealed a potential ancestral link between the catalytic subunits of microbial arsenate reductases and the protein-tyrosine phosphatases; they share similar ligands (arsenate versus phosphate) and features of their catalytic mechanism (formation of arseno-versus phospho-cysteinyl intermediates). It appears that all prokaryotic organisms, at one time, contained the genetic information necessary to construct protein phosphorylation-dephosphorylation networks that target serine, threonine, and/or tyrosine residues on proteins. However, the potential for functional redundancy among the four protein phosphatase families has led many prokaryotic organisms to discard one, two, or three of the four.

Amino Acid Sequence↗
PubMed1998

A profile of sports hand injuries in an accident and emergency department.

OBJECTIVE: To establish a profile of sports hand injuries requiring treatment in an urban accident and emergency (A&E) department, and to determine the extent to which these injuries resulted in morbidity. METHODS: A one year prospective observational study at the Royal Victoria Infirmary, Newcastle upon Tyne. All patients presenting to the A&E department between 29 July 1995 and 28 July 1996 with a hand injury sustained during sporting activity and who received follow up by A&E or plastic surgery units were enrolled. Patients were contacted by telephone or post at median of four months after injury (range two to 13) for their assessment of the outcome. RESULTS: 262 cases were enrolled into the study. The median age for males was 21 years (range 7 to 55) and for females 16 (range 9 to 40). Follow up data were obtained by telephone in 206 (79%), and by letter in a further 26 (10%). Fractures were the commonest injury (68%), followed by soft tissue injuries (20%) and dislocations (11%). The thumb was the site affected most commonly overall, and in 10 of 17 ski related injuries; next most frequent sites were little and ring fingers. Males sustained 79% of the injuries, and 54% of these occurred during football. Netball/basketball caused 63% of female injuries. Follow up indicated that mild impairment in terms of pain, stiffness, or deformity was common (45%), while the incidence of moderate pain or serious problems was 11%. CONCLUSIONS: Sporting injuries to the hand commonly require treatment in the A&E department. Telephone/postal follow up of such injuries indicates that significant short term and longer term impairment of function may result. Suitable target areas for injury prevention are secondary schools, football (in males), and netball/basketball.

Adolescent↗
PubMed1997

Protein tyrosine phosphorylation in the cyanobacterium Anabaena sp. strain PCC 7120.

Components of a protein tyrosine phosphorylation/dephosphorylation network were identified in the cyanobacterium Anabaena sp. strain PCC 7120. Three phosphotyrosine (P-Tyr) proteins of 27, 36, and 52 kDa were identified through their conspicuous immunoreactions with RC20H monoclonal antibodies specific for P-Tyr. These immunoreactions were outcompeted completely by free P-Tyr (5 mM) but not by phosphoserine or phosphothreonine. The P-Tyr content of the three major P-Tyr proteins and several minor proteins increased with their time of incubation in the presence of Mg-ATP and the protein phosphatase inhibitors sodium orthovanadate and sodium fluoride. Incubation of the same extracts with [gamma-32P]ATP but not [alpha-32P]ATP led to the phosphorylation of five polypeptides with molecular masses of 20, 27, 52, 85, and 100 kDa. Human placental protein tyrosine phosphatase 1B, with absolute specificity for P-Tyr, liberated significant quantities of 32Pi from four of the polypeptides, confirming that a portion of the protein-bound phosphate was present as 32P-Tyr. Alkaline phosphatase and the dual-specificity protein phosphatase IphP from the cyanobacterium Nostoc commune UTEX 584 also dephosphorylated these proteins and did so with greater apparent efficiency. Two of the polypeptides were partially purified, and phosphoamino analysis identified 32P-Tyr, [32P]phosphoserine, and [32P]phosphothreonine. Anabaena sp. strain PCC 7120 cell extracts contained a protein tyrosine phosphatase activity that was abolished in the presence of sodium orthovanadate and inhibited significantly by the sulfhydryl-modifying agents p-hydroxymercuriphenylsulfonic acid and p-hydroxymercuribenzoate as well as by heparin. In Anabaena sp. strain PCC 7120 the presence and/or phosphorylation status of P-Tyr proteins was influenced by incident photon flux density.

Anabaena↗
PubMed1997

Protein-tyrosine phosphorylation in the Archaea.

Sulfolobus sulfataricus ATCC 35091, Haloferax volcanii, and Methanosarcina thermophila TM-1, representing the Euryarchaeota and Crenarchaeota subdomains of the Archaea, contain proteins which are phosphorylated on tyrosine. These data raise fundamental questions as to the origin and evolution of tyrosine phosphorylation, a protein modification that is of pivotal importance in the regulation of the physiology of eukaryotic cells.

Archaea↗