scholarly journals Further studies on the role of phospholipids in determining the characteristics of mitochondrial binding sites for type I hexokinase.

2000 ◽  
Vol 47 (4) ◽  
pp. 1045-1060 ◽  
Author(s):  
J Hutny ◽  
J E Wilson
Keyword(s):  
Binding Sites ◽  
Type A ◽  
Brain Mitochondria ◽  
Bovine Brain ◽  
Type I ◽  
Type B ◽  
Acidic Phospholipids ◽  
P Type ◽  
Triton X

Previous work has indicated that two types (A and B) of binding sites for hexokinase exist, but in different proportions, on brain mitochondria from various species. Hexokinase is readily solubilized from Type A sites by glucose 6-phosphate (Glc-6-P), while hexokinase bound to Type B sites remains bound even in the presence of Glc-6-P. Type A:Type B ratios are approximately 90:10, 60:40, 40:60, and 20:80 for brain mitochondria from rat, rabbit, bovine and human brain, respectively. The present study has indicated that MgCl2-dependent partitioning of mitochondrially bound hexokinase into a hydrophobic (Triton X-114) phase is generally correlated with the proportion of Type B sites. This partitioning behavior is sensitive to phospholipase C, implying that the factor(s) responsible for conferring hydrophobic character is(are) phospholipid(s). Substantial differences were also seen in the resistance of hexokinase, bound to brain mitochondria from various species, to solubilization by Triton X-100, Triton X-114, or digitonin. This resistance increased with proportion of Type B sites. Enrichment of bovine brain mitochondria in acidic phospholipids (phosphatidylserine or phosphatidylinositol), but not phosphatidylcholine or phosphatidylethanolamine, substantially increased solubilization of the enzyme after incubation at 37 degrees C. Collectively, the results imply that the Type A and Type B sites are located in membrane domains of different lipid composition, the Type A sites being in domains enriched in acidic phospholipids which lead to greater susceptibility to solubilisation by Glc-6-P.

Feeding behaviour and bioerosion: the ecological role of the rock-boring urchin, Echinometra mathaei (de Blainville, 1825), in Okinawa reef flat

2013 ◽  
Vol 1 (1) ◽  
pp. 10
Author(s):  
Noar Muda Satyawan ◽  
Shelly Tutupoho ◽  
Yusli Wardiatno ◽  
Makoto Tsuchiya
Keyword(s):  
Feeding Behaviour ◽  
Reef Flat ◽  
Type A ◽  
Gut Contents ◽  
Biological Processes ◽  
Type B ◽  
Night Time ◽  
Echinometra Mathaei ◽  
Benthic Ecosystems

Erosion rate on corals due to activities of other biota is called bioerosion. The rock-boring urchin, Echinometra mathaei, when it is abundant, plays a significant role in benthic ecosystems, including biological processes like coral erosion. During feeding, E. mathaei erodes calcium carbonate besides grazing on algae living on coral, so it plays an important role in both organic and inorganic carbons in coral reefs. The urchin E. mathaei actively feeds during the night time (nocturnal grazer). Although in Okinawa four types (A-D) of the urchin exist, the research only focused on the types A and B. Type A of E. mathaei produced 0.44951 g feces per day on average while type B produced 0.38030 g feces per day. CaCO3 analysis in feces and gut contents showed bioerosion rate of E. mathaei type A was 0.64492 g/individu/day, and 0.54436 g/individu/day in type B. There were no significant differences in bioerosion impact of E. mathaei type A and B© Laju erosi pada karang yang disebabkan oleh biota, dikenal dengan bioerosi. Bulu babi jenis Echinometra mathaei, ketika melimpah, menjadi sangat berpengaruh terhadap ekosistem bentik termasuk proses biologi seperti erosi karang. Selama aktivitas makan, E. mathaei menggerus kalsium karbonat dalam proporsi yang besar di samping alga yang tumbuh menempel pada karang sehingga memiliki peran penting dalam siklus karbon organik dan anorganik di ekosistem terumbu karang. Bulu babi E. mathaei aktif mencari makan pada malam hari (nocturnal grazer). Meskipun di Okinanawa ada 4 tipe (A-D), pada eksperimen kali ini memfokuskan pada tipe A dan B saja. Tipe A E. mathaei rata-rata memproduksi 0,44951 g feses/hari dan tipe B memproduksi 0,38030 g feses/hari. Berdasarkan analisis CaCO3 yang dilakukan pada feses dan isi lambung, laju bioerosi yang disebabkan oleh E. mathaei tipe A sebesar 0,64492 g/individu/hari sedangkan tipe B sebesar 0,54436 g/individu/hari. Tidak terdapat perbedaan dampak bioerosi yang signifikan antara E. mathaei tipe A dan B©

scholarly journals SAT-006 A New Concept for the Endocrinology of Pre-Eclampsia: The Role of Spiral Steroids

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Fred I Chasalow ◽  
Ron Bochner
Keyword(s):  
Type A ◽  
Structural Features ◽  
Type B ◽  
Salt Diet ◽  
Breast Cyst ◽  
High K ◽  
Epithelial Na Channels ◽  
Low Salt

Abstract Background: In 1987, Graves observed that during the 3rd trimester, some patients with pre-eclampsia had high levels of unknown materials that could be detected with assays for digoxin (DLM). In 2018, we characterized a new candidate for the DLM, Ionotropin. It is a phosphocholine (PC) ester of a novel steroid with 23 carbon atoms. As Ionotropin shares structural features (a) with spironolactone (both have spiral lactones in the E-ring) and (b) with digoxin (E-ring lactone and 3α-5β configuration), we have proposed that Ionotropin may function as a potassium (K+) sparing diuretic. This suggestion is supported by the observations that [1] patients who cannot make Ionotropin (7-dehydrosterol reductase deficiency) are K+ wasting and [2] breast cyst fluids with high K+ levels also have high Ionotropin levels. Hypothesis: During the 3rd trimester, fetal requirements for K+ reach a maximum, fetal blood pressure increases and aldosterone signaling is blocked. This blockage leads to fetal sodium (Na+) wasting and is essential for formation of amniotic fluid. These events are consistent with a normal role for an unknown endogenous K+ sparing hormone and would be the basis for a modest elevation of maternal DLM during the 3rd trimester. Our hypothesis is that if any of the functions were inadequate, then the fetal-placental unit would synthesize excess PC-spiral steroids; the woman would exhibit symptoms of K+ sparing hormone excess (hypertension and proteinuria) and would be diagnosed with pre-eclampsia. Experimental Results: We have just reported a pilot study associating elevated PC esters of spiral steroids in women with pre-eclampsia. In brief, 12 of 19 women had elevated levels of at least one of the PC steroids (Z-score > 2) when compared to the levels in 20 pregnant women matched for gestational age and fetal sex. There are two basic mechanisms for this dichotomy: (a) there may be episodic secretion with of a DLM with a short half-life or (b) there may be two different underlying biochemical causes. In prior studies, there has been no indication of episodic secretion of DLM similar to that observed with glucocorticoids, Ionotropin or other PC spiral steroids. Discussion: There are two basic types of K+ sparing diuretics. Type A: Spironolactone functions by regulating the NaK-ATPase. Type B: Triamterene functions by blocking synthesis of epithelial Na+ channels. Thus, Type A would have high levels of spiral steroids and Type B would have low levels of spiral steroids. Type A patients would be expected to have higher risk of long-term consequences when compared to the Type B patients. Conclusion: The recognition of the division of pre-eclampsia into two separate diseases might be the key observation for developing Type-specific diagnosis and therapy. For example, a Type A patient might benefit from a low salt diet but that diet would not be expected to benefit a patient with Type B disease.

scholarly journals The role of ADP in the modulation of the calcium-efflux pathway in rat brain mitochondria

1985 ◽  
Vol 225 (1) ◽  
pp. 41-49 ◽  
Author(s):  
J Vitorica ◽  
J Satrústegui
Keyword(s):  
Rat Brain ◽  
Binding Sites ◽  
Tricarboxylic Acid Cycle ◽  
Brain Mitochondria ◽  
Ruthenium Red ◽  
Calcium Efflux ◽  
Rat Brain Mitochondria ◽  
Pi Complex ◽  
Efflux Pathway

The role of ADP in the regulation of Ca2+ efflux in rat brain mitochondria was investigated. ADP was shown to inhibit Ruthenium-Red-insensitive H+- and Na+-dependent Ca2+-efflux rates if Pi was present, but had no effect in the absence of Pi. The primary effect of ADP is an inhibition of Pi efflux, and therefore it allows the formation of a matrix Ca2+-Pi complex at concentrations above 0.2 mM-Pi and 25 nmol of Ca2+/mg of protein, which maintains a constant free matrix Ca2+ concentration. ADP inhibition of Pi and Ca2+ efflux is nucleotide-specific, since in the presence of oligomycin and an inhibitor of adenylate kinase ATP does not substitute for ADP, is dependent on the amount of ADP present, and requires ADP concentrations in excess of the concentrations of translocase binding sites. Brain mitochondria incubated with 0.2 mM-Pi and ADP showed Ca2+-efflux rates dependent on Ca2+ loads at Ca2+ concentrations below those required for the formation of a Pi-Ca2+ complex, and behaved as perfect cytosolic buffers exclusively at high Ca2+ loads. The possible role of brain mitochondrial Ca2+ in the regulation of the tricarboxylic acid-cycle enzymes and in buffering cytosolic Ca2+ is discussed.

scholarly journals Cytokinin induces genome-wide binding of the type-B response regulator ARR10 to regulate growth and development in Arabidopsis

2017 ◽  
Vol 114 (29) ◽  
pp. E5995-E6004 ◽  
Author(s):  
Yan O. Zubo ◽  
Ivory Clabaugh Blakley ◽  
Maria V. Yamburenko ◽  
Jennifer M. Worthen ◽  
Ian H. Street ◽  
...  
Keyword(s):  
Protein Binding ◽  
Binding Sites ◽  
Growth And Development ◽  
Abiotic Factors ◽  
Physiological Responses ◽  
Physiological Role ◽  
Primary Response ◽  
Type B ◽  
Protein Binding Microarrays

The plant hormone cytokinin affects a diverse array of growth and development processes and responses to the environment. How a signaling molecule mediates such a diverse array of outputs and how these response pathways are integrated with other inputs remain fundamental questions in plant biology. To this end, we characterized the transcriptional network initiated by the type-B ARABIDOPSIS RESPONSE REGULATORs (ARRs) that mediate the cytokinin primary response, making use of chromatin immunoprecipitation sequencing (ChIP-seq), protein-binding microarrays, and transcriptomic approaches. By ectopic overexpression of ARR10, Arabidopsis lines hypersensitive to cytokinin were generated and used to clarify the role of cytokinin in regulation of various physiological responses. ChIP-seq was used to identify the cytokinin-dependent targets for ARR10, thereby defining a crucial link between the cytokinin primary-response pathway and the transcriptional changes that mediate physiological responses to this phytohormone. Binding of ARR10 was induced by cytokinin with binding sites enriched toward the transcriptional start sites for both induced and repressed genes. Three type-B ARR DNA-binding motifs, determined by use of protein-binding microarrays, were enriched at ARR10 binding sites, confirming their physiological relevance. WUSCHEL was identified as a direct target of ARR10, with its cytokinin-enhanced expression resulting in enhanced shooting in tissue culture. Results from our analyses shed light on the physiological role of the type-B ARRs in regulating the cytokinin response, mechanism of type-B ARR activation, and basis by which cytokinin regulates diverse aspects of growth and development as well as responses to biotic and abiotic factors.

Identification of Heparin-Binding Sites in the Fibronectin Type III Domains of the Leukocyte Common Antigen (CD45)

2004 ◽  
Vol 69 (3) ◽  
pp. 645-658
Author(s):  
Daniel Kavan ◽  
Markéta Vančurová ◽  
Dana Ulbrichová ◽  
Ivana Hladíková ◽  
Miloslav Pospíšil ◽  
...  
Keyword(s):  
Binding Sites ◽  
Tyrosine Phosphatase ◽  
Type I ◽  
Heparin Binding ◽  
Membrane Glycoproteins ◽  
Type Iii ◽  
Definitive Evidence ◽  
Rich Domain ◽  
Fibronectin Domains

Leukocyte common antigens (CD45) are large receptors that are abundantly expressed at the surface of all leukocytes. These receptors are type I membrane glycoproteins possessing two large C-terminal intracellular domains with protein tyrosine phosphatase activity. While the role of these enzyme domains in leukocyte signaling is well documented, the role of the N-terminal extracellular portion of CD45, composed of sequences formed by alternatively spliced exons, the cysteine rich domain, and three type III fibronectin repeats, remains unclear. The presence of fibronectin domains would predict the occurrence of heparin-binding sites, which may account for the documented affinity of CD45 for acid polysaccharides. We addressed this hypothesis using soluble recombinant proteins corresponding to the individual fibronectin domains (FN1 to FN3), and to the entire extracellular portion of CD45 (sCD45). Binding of these proteins to heparin was examined by frontal affinity chromatography. We found that while the sCD45 bound to heparin with Kd of 3.2 × 10-8 mol/l, the binding of FN2 and FN3 was somewhat weaker (Kd was 1.4 and 7.4 × 10-7 mol/l, respectively). The FN1 domain did not interact with heparin. Our results bring definitive evidence for the existence of binding sites for acid polysaccharides in the extracellular domain of CD45. These binding sites may be important for surface interactions of CD45 and for leukocyte signaling.

Characterization of type A and type B CCK receptor binding sites in rat vagus nerve

1993 ◽  
Vol 623 (1) ◽  
pp. 161-166 ◽  
Author(s):  
Eric S. Corp ◽  
Jennifer McQuade ◽  
Timothy H. Moran ◽  
Gerard P. Smith
Keyword(s):  
Vagus Nerve ◽  
Receptor Binding ◽  
Binding Sites ◽  
Type A ◽  
Type B

The Role of Type A Behaviour Pattern in Chronic Headache

1988 ◽  
Vol 5 (1) ◽  
pp. 3-8 ◽  
Author(s):  
Joel J. Hillhouse ◽  
Edward B. Blanchard ◽  
Kenneth A. Appelbaum ◽  
Cynthia Kirsch
Keyword(s):  
Chronic Headache ◽  
Type A ◽  
Behaviour Pattern ◽  
Type B ◽  
Daily Diaries ◽  
Dependent Variables ◽  
Headache Type ◽  
Activity Survey

Chronic headache sufferers (N = 133) were assessed for Type A behaviour pattern using the Jenkins Activity Survey (JAS). The Type A score frequency distribution for all headache subjects combined, and each headache type separately were examined. Median scores of the all subjects combined group fell into the indeterminate range of Type A scores, that is, neither Type A or Type B. This was also the case for migraine and tension sufferers. Mixed subject's scores fell into the range of scores usually classified as Type A. Forty-five percent of the mixed subjects fit the criteria for Type A behaviour pattern. Follow-up bivariate and multivariate analysis using J AS subscale scores as independent predictors and headache activity scores, from daily diaries, as dependent variables revealed only three correlations which approached significance. These results argue against a clear linear relationship between chronic headache and Type A behaviour pattern. There may be some utility in this construct when differentiated by headache type.

scholarly journals Desmoglein 2 regulates cardiogenesis by restricting hematopoiesis in the developing murine heart

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hoda Moazzen ◽  
Kateryna Venger ◽  
Sebastian Kant ◽  
Rudolf E. Leube ◽  
Claudia A. Krusche
Keyword(s):  
Heart Development ◽  
Type A ◽  
Regulatory Role ◽  
Structural Defects ◽  
Intercellular Signaling ◽  
Type B ◽  
Cell Clusters ◽  
Cardiac Wall ◽  
Myocardial Wall

AbstractCardiac morphogenesis relies on intricate intercellular signaling. Altered signaling impacts cardiac function and is detrimental to embryonic survival. Here we report an unexpected regulatory role of the desmosomal cell adhesion molecule desmoglein 2 (Dsg2) on murine heart development. A large percentage of Dsg2-mutant embryos develop pericardial hemorrhage. Lethal myocardial rupture is occasionally observed, which is not associated with loss of cardiomyocyte contact but with expansion of abnormal, non-myocyte cell clusters within the myocardial wall. Two types of abnormal cell clusters can be distinguished: Type A clusters involve endocard-associated, round-shaped CD31+ cells, which proliferate and invade the myocardium. They acquire Runx1- and CD44-positivity indicating a shift towards a hematopoietic phenotype. Type B clusters expand subepicardially and next to type A clusters. They consist primarily of Ter119+ erythroid cells with interspersed Runx1+/CD44+ cells suggesting that they originate from type A cell clusters. The observed pericardial hemorrhage is caused by migration of erythrocytes from type B clusters through the epicardium and rupture of the altered cardiac wall. Finally, evidence is presented that structural defects of Dsg2-depleted cardiomyocytes are primary to the observed pathogenesis. We propose that cardiomyocyte-driven paracrine signaling, which likely involves Notch1, directs subsequent trans-differentiation of endo- and epicardial cells. Together, our observations uncover a hitherto unknown regulatory role of Dsg2 in cardiogenesis.

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