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P S Agutter

Publications and source records attributed to P S Agutter.

48 records · Page 3Linked to original sources
PubMed1977

Ribonucleic acid stimulation of mammalian liver nuclear-envelope nucleoside triphosphatase. A possible enzymic marker for the nuclear envelope.

1. The specific activity of rat and pig liver nuclear-envelope nucleoside triphosphatase (EC 3.6.1.3) decreases when the system is depleted of RNA. The activity can be restored by adding high concentrations of yeast RNA to the assay medium. 2. Exogenous RNA also increases the activity of the enzyme in control envelopes (not RNA-depleted). The effect appears to be largely specific for poly(A) and poly(G); it is not stimulated by rRNA or tRNA preparations, ribonuclease-hydrolysed RNA, AMP, or double- or single-stranded DNA. 3. Inhibitors of the enzyme, in concentrations at which half-maximal inhibition of the enzyme is achieved, do not affect the percentage stimulation of the enzyme by yeast RNA. 4. The simulation is abolished by the inclusion of 150 mM-KCl or -NaCl in the assay medium, but not by increasing the assay pH to 8.5. 5. The results are discussed in the light of the possible role of the nucleoside triphosphatase in vivo in nucleo-cytoplasmic ribonucleoprotein translocation. 6. It is proposed that poly(G)-stimulated Mg2+-activated adenosine triphosphatase activity should be adopted as an enzymic marker for the nuclear envelope.

Adenosine Triphosphatases↗
PubMed1977

Changes in the activities of some membrane-associated enzymes during in vivo ageing of the normal human erythrocyte.

Human erythrocytes from healthy male donors were fractionated with respect to in vivo age by simple centrifugation in order to characterize changes in the functional integrity of the membrane during the life-span of the cell. The three enzymes, Na/K-ATPase, glyceraldehyde-3-phosphate dehydrogenase and NADH-ferricyanide reductase, were found not to change with age, but significant age-dependent decreases were observed in the cases of acetylcholinesterase, phosphoglycerate kinase, purine nucleoside phosphorylase, adenylate kinase, Mg-ATPase and alkaline phosphatase. The possibility that these changes were attributable to mechanisms other than age-related inactivation, such as reticulocyte contamination, differential resealing and crypticity, was investigated. Only the decrease in acetylcholinesterase could be explained wholly in terms of reticulocyte contamination. A decrease in membrane integrity on ageing was observed, which accounted for approximately half the change in alkaline phosphatase and may have contributed to the other enzyme activity changes. This membrane integrity effect masked a real decrease in the highly cryptic NADH-ferricyanide reductase, this decrease being apparent only after total disaggregation of the membrane with nonionic surfactant.

Acetylcholinesterase↗
PubMedDate not supplied

[Age-dependent changes in mRNA transport (nucleus-cytoplasm)].

Transport of mRNA from nucleus to cytoplasm is an ATP-dependent process which occurs strictly vectorially. Because the mRNA is structurally bound during transport, mRNA transport is a "solid-state" process consisting of i) mRNA release from the nuclear matrix, ii) mRNA translocation through the nuclear pore, and iii) cytoskeletal binding. We identified and purified the following components involved in the translocation step: i) the nuclear envelope (NE) nucleoside triphosphatase (NTPase) which is stimulated by the 3'poly(A) tail of mRNA, ii) the poly(A)-recognizing mRNA carrier, iii) the NE protein kinase, and iv) the NE phosphatase. In addition, we found that an RNA helicase activity is present in NE, which also may be involved in RNA transport. Our results show that, besides poly(A), also double-stranded RNA structures may modulate RNA export. The amount of mRNA released from nuclei markedly decreases with age. Evidence is presented that this age-dependent change is caused by an impairment of polyadenylation of mRNA, hnRNA processing, release of mRNA from nuclear matrix, and translocations of mRNA from nuclear to cytoplasmic compartment (decrease in activities of NE NTPase, protein kinase, and phosphatase; decrease in poly(A)-binding affinity of mRNA carrier).

Animals↗