title: Ribonucleases in bacterial toxin–antitoxin systems

authors: Cook, Gregory M.

subjects: Endoribonucleases

abstract: Toxin-antitoxin (TA) systems are widespread in bacteria and archaea and play important roles in a diverse range of cellular activities. TA systems have been broadly classified into 5 types and the targets of the toxins are diverse, but the most frequently used cellular target is mRNA. Toxins that target mRNA to inhibit translation can be classified as ribosome-dependent or ribosome-independent RNA interferases. These RNA interferases are sequence-specific endoribonucleases that cleave RNA at specific sequences. Despite limited sequence similarity, ribosome-independent RNA interferases belong to a limited number of structural classes. The MazF structural family includes MazF, Kid, ParE and CcdB toxins. MazF members cleave mRNA at 3-, 5- or 7-base recognition sequences in different bacteria and have been implicated in controlling cell death (programmed) and cell growth, and cellular responses to nutrient starvation, antibiotics, heat and oxidative stress. VapC endoribonucleases belong to the PIN-domain family and inhibit translation by either cleaving tRNAfMet in the anticodon stem loop, cleaving mRNA at -AUA(U/A)-hairpin-G- sequences or by sequence-specific RNA binding. VapC has been implicated in controlling bacterial growth in the intracellular environment and in microbial adaptation to nutrient limitation (nitrogen, carbon) and heat shock. ToxN shows structural homology to MazF and is also a sequence-specific endoribonuclease. ToxN confers phage resistance by causing cell death upon phage infection by cleaving cellular and phage RNAs, thereby interfering with bacterial and phage growth. Notwithstanding our recent progress in understanding ribonuclease action and function in TA systems, the environmental triggers that cause release of the toxin from its cognate antitoxin and the precise cellular function of these systems in many bacteria remain to be discovered. This article is part of a Special Issue entitled: RNA Decay mechanisms.

text: Ribonucleases in bacterial toxin–antitoxin systems Toxin-antitoxin (TA) systems are widespread in bacteria and archaea and play important roles in a diverse range of cellular activities. TA systems have been broadly classified into 5 types and the targets of the toxins are diverse, but the most frequently used cellular target is mRNA. Toxins that target mRNA to inhibit translation can be classified as ribosome-dependent or ribosome-independent RNA interferases. These RNA interferases are sequence-specific endoribonucleases that cleave RNA at specific sequences. Despite limited sequence similarity, ribosome-independent RNA interferases belong to a limited number of structural classes. The MazF structural family includes MazF, Kid, ParE and CcdB toxins. MazF members cleave mRNA at 3-, 5- or 7-base recognition sequences in different bacteria and have been implicated in controlling cell death (programmed) and cell growth, and cellular responses to nutrient starvation, antibiotics, heat and oxidative stress. VapC endoribonucleases belong to the PIN-domain family and inhibit translation by either cleaving tRNAfMet in the anticodon stem loop, cleaving mRNA at -AUA(U/A)-hairpin-G- sequences or by sequence-specific RNA binding. VapC has been implicated in controlling bacterial growth in the intracellular environment and in microbial adaptation to nutrient limitation (nitrogen, carbon) and heat shock. ToxN shows structural homology to MazF and is also a sequence-specific endoribonuclease. ToxN confers phage resistance by causing cell death upon phage infection by cleaving cellular and phage RNAs, thereby interfering with bacterial and phage growth. Notwithstanding our recent progress in understanding ribonuclease action and function in TA systems, the environmental triggers that cause release of the toxin from its cognate antitoxin and the precise cellular function of these systems in many bacteria remain to be discovered. This article is part of a Special Issue entitled: RNA Decay mechanisms.

year: 2013

title: A cell-associated oligo-1,6-alpha-glucosidase from an extremely thermophilic anaerobic bacterium, Thermoanaerobium Tok6-B1.

authors: Plant, Adrian R.

subjects: biology

abstract: Cell-associated oligo-1,6-alpha-glucosidase (EC 3.2.1.10) was isolated from Thermoanaerobium Tok6-B1 grown on starch-containing medium. Activity was purified 11.4-fold by salt precipitation, gel filtration, hydroxyapatite and anion-exchange chromatography. Molecular mass was determined as 30,000 by SDS/polyacrylamide-gel electrophoresis and 33,000 by analytical gel filtration. The probable order of specificity was p-nitrophenyl-alpha D-glucose greater than-isomaltose greater than-isomaltotriose greater than-panose greater than-nigerose and no activity was shown against malto-oligosaccharides, melezitose, melibiose, raffinose, cellobiose, sophorose, gentiobiose, lactose, pullulan, dextran or amylose. The optima for activity and stability were between pH 5.6 and 7.0 and the half-life at pH 6.5 was 1000 min at 70 degrees C and 20 min at 76 degrees C. Activity was stabilized by substrate, Mg2+, Mn2+ and Ca2+, but was destabilized by Zn2+ and EDTA. N-Ethylmaleimide, glucose and 1-O-methyl-alpha D-glucose were inhibitory but 1-O-methyl-beta D-glucose stimulated activity. The activation energy (Ea) was 109 kJ/mol.

text: A cell-associated oligo-1,6-alpha-glucosidase from an extremely thermophilic anaerobic bacterium, Thermoanaerobium Tok6-B1. Cell-associated oligo-1,6-alpha-glucosidase (EC 3.2.1.10) was isolated from Thermoanaerobium Tok6-B1 grown on starch-containing medium. Activity was purified 11.4-fold by salt precipitation, gel filtration, hydroxyapatite and anion-exchange chromatography. Molecular mass was determined as 30,000 by SDS/polyacrylamide-gel electrophoresis and 33,000 by analytical gel filtration. The probable order of specificity was p-nitrophenyl-alpha D-glucose greater than-isomaltose greater than-isomaltotriose greater than-panose greater than-nigerose and no activity was shown against malto-oligosaccharides, melezitose, melibiose, raffinose, cellobiose, sophorose, gentiobiose, lactose, pullulan, dextran or amylose. The optima for activity and stability were between pH 5.6 and 7.0 and the half-life at pH 6.5 was 1000 min at 70 degrees C and 20 min at 76 degrees C. Activity was stabilized by substrate, Mg2+, Mn2+ and Ca2+, but was destabilized by Zn2+ and EDTA. N-Ethylmaleimide, glucose and 1-O-methyl-alpha D-glucose were inhibitory but 1-O-methyl-beta D-glucose stimulated activity. The activation energy (Ea) was 109 kJ/mol.

year: 1988

title: Māori and medications: What happens when the pills go home?

authors: Nikora, Linda Waimarie

subjects: Māori

abstract: Chronic illnesses are a feature of many Māori homescapes. These illnesses are often managed at home through the use of health technologies, particularly medications. This article explores the meanings given to medications and the use of this health technology in four Māori households. We use a range of qualitative methods to engage with householders and to document how medications are acculturated into Māori homescapes and everyday lives. From our discussions with householders about the procurement, storage, emplacement and administration of medications emerged five culturally patterned orientations to treating with medications. They are: 1) storage and administration practices that corresponded with the Māori hygiene practices of tapu (prohibited) and noa (permitted); 2) reminder strategies, or ngā pūrere whakamāharahara; 3) the enactment of the value of manaakitanga (kindness) in care relationships; 4) pōharatanga, or attitudes towards medication procurement and administration in households textured by low socio-economic status; and 5) rangatiratanga, the right of people to manage and make decisions about their own lives and health status. This study presents a view of how medications are acculturated into Māori homescapes, relationships and daily routines. The use of health technologies by health professionals to interrupt illness and improve quality of life must be cognisant of the cultural contexts into which medications are prescribed.

text: Māori and medications: What happens when the pills go home? Chronic illnesses are a feature of many Māori homescapes. These illnesses are often managed at home through the use of health technologies, particularly medications. This article explores the meanings given to medications and the use of this health technology in four Māori households. We use a range of qualitative methods to engage with householders and to document how medications are acculturated into Māori homescapes and everyday lives. From our discussions with householders about the procurement, storage, emplacement and administration of medications emerged five culturally patterned orientations to treating with medications. They are: 1) storage and administration practices that corresponded with the Māori hygiene practices of tapu (prohibited) and noa (permitted); 2) reminder strategies, or ngā pūrere whakamāharahara; 3) the enactment of the value of manaakitanga (kindness) in care relationships; 4) pōharatanga, or attitudes towards medication procurement and administration in households textured by low socio-economic status; and 5) rangatiratanga, the right of people to manage and make decisions about their own lives and health status. This study presents a view of how medications are acculturated into Māori homescapes, relationships and daily routines. The use of health technologies by health professionals to interrupt illness and improve quality of life must be cognisant of the cultural contexts into which medications are prescribed.

year: 2011