Febs Letters

doi: 10.1016/0014-5793(88)80689-6pmid: N/A

Appella, Ettore; Weber, Irene T.; Blasi, Francesco

doi: 10.1016/0014-5793(88)80690-2pmid: 3282918

Kosower, Edward M.

doi: 10.1016/0014-5793(88)80691-4pmid: 2834229

Based on the nicotinic acetylcholine receptor model [(1987) Eur. J. Biochem. 168, 431–449], a partial model is constructed for the exobilayer portion of the GABAA receptor, an approach justified by the superfamily relationship of the two receptors [(1987) Nature 328, 221–227]. The model predicts succesfully the excess positive charge on interior strands which constitute the ligand‐responsive portion of the receptor. Binding to GABA expands the exobilayer portion of the receptor, opening a pathway to a chloride channel. Separate binding sites for antianxiolytics (benzodiazepines) and hypnotics (barbiturates) are suggested, with prolongation of chloride entry projected as a consequence of stabilization of the open form. The anion‐exchange protein (AEP) of membranes (band 3 of red blood cell membranes) is similar in some respects to the γ‐aminobutyric acid (GABAA) receptor. Both proteins are inhibited and labeled by diisocyanatostilbenedisulfonate (DIDS), both transport Cl− and HCO− 3, and both are membrane proteins. Starting with the lysines known to be labeled in band 3 protein, searches of the amino acid sequences of the GABAA receptor α‐ and β‐subunits reveal at least 4 reasonably homologous sequences. The relationship between AEP and GABAA receptor leads to the idea that the chloride/bicarbonate channel may be the ancestor of all ligand‐gated channels, with ligand gating by γ‐aminobutyric acid and acetylcholine arising later in evolution.

Boudot, Denis; Canet, Daniel; Brondeau, Jean; Martin, Francis

doi: 10.1016/0014-5793(88)80692-6pmid: N/A

The simplest pulse sequence (π/2)x—τ— (π/2)y (Acquisition) for nuclear spin polarization transfer is used in a selective fashion: transfer only flows from a nucleus A to any nucleus X J‐coupled to A, provided that the carrier frequency coincides with the A resonance and that τ is slightly varied around a properly chosen value, relevant free induction decays being co‐added. According to the value selected for τ (1/2J or 1/4J, J: one bond carbon‐carbon coupling constant), it proves possible to sort out and compare subspectra pertaining to isotopomers involving one, two, three, and four consecutive 13C. The method has been applied to an extract of mycelium grown on a medium containing 13C‐labeled acetate, with the aim of delineating metabolic pathways from proportions of the detected isotopomers.

Barnard, Glenn N.; Sanders, Jeremy K.M.

doi: 10.1016/0014-5793(88)80693-8pmid: N/A

13C‐NMR spectra of whole native cells of Methylobacterium AM1 show dominant signals belonging to poly(β‐hydroxybutyrate) and trehalose. Fractionation of the cells demonstrates that the poly(β‐hydroxybutyrate) is located in the storage granules and that the trehalose is located in the cytosol. The observation of relatively sharp poly(β‐hydroxybutyrate) signals indicates that the polymer granule in this organism is in a mobile rather than truly solid state in vivo.

Berry, M.N.; Gregory, R.B.; Grivell, A.R.; Henly, D.C.; Phillips, J.W.; Wallace, P.G.; Welch, G.R.

doi: 10.1016/0014-5793(88)80694-Xpmid: 2966075

We have studied the stimulatory effects of palmitate on the rate of glucose synthesis from lactate in isolated hepatocytes. Control of the metabolic flow was achieved by modulating the activity of enolase using graded concentrations of fluoride. Unexpectedly, palmitate stimulated gluconeogenesis even when enolase was rate‐limiting. This stimulation was also observed when the activities of phosphoenolpyruvate carboxykinase and aspartate aminotransferase were modulated using graded concentrations of quinolinate and aminooxyacetate, respectively. Linear force‐flow relationships were found between the rate of gluconeogenesis and indicators of cellular energy status (i.e. mitochondrial membrane and redox potentials and cellular phosphorylation potential). These findings suggest that the fatty acid stimulation of glucose synthesis is in part mediated through thermodynamic mechanisms.

Furmaniak, J.; Talbot, D.; Reinwein, D.; Benker, G.; Creagh, F.M.; Smith, B.Rees

doi: 10.1016/0014-5793(88)80695-1pmid: 3360129

Human adrenal microsomes have been labelled with 125I and immunoprecipitated with sera from patients with Addison's disease. The immunoprecipitates were then analysed by SDS‐PAGE and autoradiography. 13 of the 23 sera from the Addison patients studied contained antibodies which reacted with a 55 kDa adrenal microsomal protein. The same 13 sera were also positive for adrenal antibodies as judged by immunofluorescence. The 55 kDa protein was not immunoprecipitated from placenta or thyroid microsomes by Addison sera. Furthermore, patients with Graves' disease or rheumatoid arthritis did not immunoprecipitate the 55 kDa protein from adrenal microsomes. Our studies suggest therefore that Addison sera contain antibodies to a 55 kDa adrenal specific protein which may well be the antigen observed on immunofluorescence.

Tsunoda, Yasuhiro; Yodozawa, Susumu; Tashiro, Yutaka

doi: 10.1016/0014-5793(88)80696-3pmid: 3258830

The myo‐inositol 1,4,5‐trisphosphate (IP3)‐induced Ca2+ mobilization in single saponin‐permeabilized and fura‐2‐loaded parietal cells was analysed by a fluorescence digital image processor. When the cells were incubated with ATP, free cytoplasmic Ca2+ concentration ([Ca2+]i) increased in some restricted cytoplasmic regions showing discontinuous plateau and in the peripheral cytoplasm showing continuous [Ca2+]i gradient towards the plasma membranes. When treated with IP3, the high plateau enlarged to the entire cytoplasm and (a) new higher plateau(s) appeared and enlarged again in a transient manner. The IP3‐induced Ca2+ transient was also observed by fluorescence microphotometry of the single cells or by fluorescence spectrophotometry and 45Ca2+ uptake experiment of the cell population.

Udvardi, Michael K.; Price, G.Dean; Gresshoff, Peter M.; Day, David A.

doi: 10.1016/0014-5793(88)80697-5pmid: N/A

Using preparations of peribacteroid membrane (PBM)‐enclosed bacteroids from soybean root nodules, we show here that the PBM possesses a dicarboxylate transporter capable of mediating a rapid flux of dicarboxylate anions, such as malate and succinate, to the bacteroids inside the nodule. The transporter has a higher affinity for the monovalent malate anion than for the succinate anion (K m = 2 and 15 μM, respectively) although the V max for malate− appears to be lower than for succinate− (V max = 11 and 30 nmol·min−1·mg protein−1, respectively).

Kiss, Zoltan; Deli, Eva; Kuo, J.F.

doi: 10.1016/0014-5793(88)80698-7pmid: 3162885

Immunocytochemical methods were used to study protein kinase C (PKC) distribution in HL60 cells during the entire course of 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA)‐induced differentiation. After an initial translocation of PKC from cytoplasm to plasma membrane, the enzyme was localized close to the nuclear membrane region at day 1 of TPA treatment. PKC was associated with nuclei at day 2 and with nuclei, cytoplasm and plasma membrane at days 3 and 5. Attachment of cells to substratum (day 2) was accompanied by increased phosphorylation of several nuclear proteins. At day 7, the differentiated cells became detached and PKC in these cells was largely cytoplasmic. In view of the crucial role of PKC in cell differentiation, it is expected that changes in its intracellular localization have physiological significance.