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131.
Stephen A. Baldwin Jocelyn M. Baldwin Frank R. Gorga Gustav E. Lienhard 《生物化学与生物物理学报:生物膜》1979,552(1):183-188
The cytochalasin B binding component of the human erythrocyte monosaccharide transport system has been purified. The preparation appears to contain one major protein with an apparent polypeptide chain molecular weight of 55 000 and about 0.4 binding sites per chain. Cytochalasin B binds to the reconstituted preparation with a dissociation constant of 1.3·10?7 M, a value which is similar to that reported for the transport system in the intact erythrocyte. 相似文献
132.
Evidence from the kinetics of transport supports the hypothesis that cellular Li, Lic, interacts with the internal aspect of the (Na,K)-pump as a congener of Na, Lic and Nac compete for the same sites on the internal aspect of the pump. Lic promotes Na-activated K influx and Nac promotes Li-activated K influx. Cellular K inhibits Li-activated K influx, indicating that the interaction of Kc with the internal aspect of the pump is qualitatively different from the interaction with either Nac or Lic. The Hill coefficients for Na-promoted and Li-promoted K influx are similar and are both greater than unity, indicating the same number of multiple intracellular sites per pump for the two cations. The stoichiometry of coupling between efflux and K influx is also similar for Na and Li, and is close to 3 Na or 3 Li to 2 K. The Li-activated K influx appears to be independent of the residual Na which remains in cells prepared in Na-free solutions. 相似文献
133.
Mario M. Moronne Rolf J. Mehlhorn Michael P. Miller Larry C. Ackerson Robert I. Macey 《The Journal of membrane biology》1990,115(1):31-40
Summary Red cell water volumes were measured using ESR methods during transient osmotic perturbation, and under equilibrium conditions. Cell water contents were determined using the spin label Tempone (2,2,6,6-tetramethyl piperidine-N-oxyl) and the membrane impermeable quencher potassium chromium oxalate. With appropriate corrections for intracellular viscosity and changes in cavity sensitivity, equilibrium cell water measured both by electron spin resonance (ESR) and wet minus dry weight methods gave excellent agreement in solutions from 243–907 mOsm. Intracellular viscosities determined from the Tempone correlation times in the same cells gave values ranging from 9–47 centipoise at 21°C.Osmotically induced transient volume changes were measured using Tempone and an ESR stopped-flow configuration. The Tempone response time was estimated at 17 msec compared to 250–350 msec for normal water relaxations. Nonlinear least square solutions to the Kedem-Katchalsky equations including a correction for the finite Tempone permeability gave 0.029 and 0.030 cm/sec for the osmotic permeability of RBCs in swell and shrink experiments, respectively. In stopped-flow experiments accurate water flux data are obtained very soon after challenging cells and do not require baseline subtractions. These results represent significant improvements over conventional light scattering techniques which necessitate corrections for long lasting optical artifacts (200–300 msec), and baseline drifts. 相似文献
134.
A study has been carried out into the effects of clinically important general anaesthetics, althesin, thiopentone and propanidid, on the transport of glucose and phosphate across the membrane of the human erythrocyte. In general these three substances all inhibit both transport processes but with characteristic inhibition profiles and varying degrees of efficacy. Glucose transport was more sensitive to the hydrophobic steroids and phosphate transport to propanidid. Some hydrophobic agents, e.g., iodobenzene and its azide, were not inhibitory. Removal of cholesterol to some extent augmented the inhibitory effects of most of these compounds (not propanidid). It is argued that these effects are due to the penetration of the anaesthetics into the lipid bilayer and either subsequent disruption of the lipid annuli surrounding the integral membrane proteins and/or direct anaesthetic-protein interaction. 相似文献
135.
Especially in childhood, the in vivo action of microbial neuraminidase may cause haemolytic anaemia or life-threatening haemolytic
uraemic syndrome. The exposure of the Thomsen-Friedenreich (T) crypto-antigen and T-antigen polyagglutinability of erythrocytes
has been described as the first sign of toxic cleavage of N-acetylneuraminic acid (Neu5Ac) from sialoglycoproteins of cell
membranes. This phenomenon may, however, be too unspecific to initiate treatment for toxin elimination. The present study
investigated the diagnostic effectiveness of a panel of three monoclonal antibodies (mcabs) for the estimation of the clinical
significance of neuraminidase action in vivo. Depending on the amount of Neu5Ac released, the mcabs I-C4, II-Q9 and III-Y12
recognized different epitopes on erythrocyte asialoglycophorin. In 1345 patients, the mcab II-Q9 detected cleavage of Neu5Ac
in 32 children who had T-antigen polyagglutinability and mild to moderate haemolytic anaemia. However, only 10 patients, whose
erythrocytes were agglutinated by the mcabs III-Y12 or I-C4, developed severe haemolysis, thrombocytopenia, and finally the
life-threatening haemolytic uraemic syndrome (p<0.0002). In conclusion, these mcabs provided an early marker of the in vivo
action of neuraminidase. Two different degrees of erythrocyte desialylation, as defined by these mcabs, are suggested to reflect
the severity of toxin-associated disease.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
136.
Dallas M. Cowan Qiyuan Fan Yan Zou Xiujuan Shi Jian Chen Michael Aschner 《Biomarkers》2013,18(1):3-16
Unexposed control subjects (n = 106), power distributing and office workers (n = 122), and manganese (Mn)-exposed ferroalloy smelter workers (n = 95) were recruited to the control, low and high groups, respectively. Mn concentrations in saliva, plasma, erythrocytes, urine and hair were significantly higher in both exposure groups than in the controls. The Fe concentration in plasma and erythrocytes, however, was significantly lower in Mn-exposed workers than in controls. The airborne Mn levels were significantly associated with Mn/Fe ratio (MIR) of erythrocytes (eMIR) (r = 0.77, p < 0.01) and plasma (pMIR) (r = 0.70, p < 0.01). The results suggest that the MIR may serve as a useful biomarker to distinguish Mn-exposed workers from the unexposed, control population. 相似文献
137.
Naotaka Hamasaki Kenji Izuhara Kenshi Okubo Yoko Kanazawa Akira Omachi Robert A. Kleps 《The Journal of membrane biology》1990,116(1):87-91
Summary The line widths of35Cl– nuclear magnetic resonances were used to measure chloride binding by Band 3. Since this procedure related directly to binding, the data obtained may be interpreted more unequivocally than affinities derived from kinetic data which could be related to either translocation or binding. Chloride binding to the active sites in Band 3 was assessed from that portion of the total line width which was sensitive to 4,4-dinitrostilbene-2,2-disulfonic acid. These sites appeared to be completely inhibited by treatment of erythrocyte membranes with diethylpyrocarbonate. This result is consistent with our previous observation that this reagent inhibits anion transport in resealed erythrocyte ghosts (Izuhara, Okubo & Hamasaki, 1989,Biochemistry
28:4725–4728). Hydroxylamine could not reverse the diethylpyrocarbonate inhibition of chloride binding to Band 3. The pH-dependence of diethylpyrocarbonate reactivity suggests that the modified residues may be those of histidine. 相似文献
138.
Mitzy Canessa Mary E. Fabry Sandra M. Suzuka Kevin Morgan Ronald L. Nagel 《The Journal of membrane biology》1990,116(2):107-115
Summary Red cell volume regulation is important in sickle cell anemia because the rate and extent of HbS polymerization are strongly dependent on initial hemoglobin concentration. We have demonstrated that volume-sensitive K:Cl cotransport is highly active in SS whole blood and is capable of increasing MCHC. We now report that Na+/H+ exchange (Na/H EXC), which is capable of decreasing the MCHC of erythrocytes with pHi<7.2, is also very active in the blood of patients homozygous for HbS. The activity of Na/H EXC (maximum rate) was determined by measuring net Na+ influx (mmol/liter cell·hr=FU) driven by an outward H+ gradient in oxygenated, acidloaded (pHi 6.0), DIDS-treated SS cells. The Na/H EXC activity was 33±3 FU (mean±se) (n=19) in AA whites, 37±8 FU (n=8) in AA blacks, and 85±15 FU (n=14) in SS patients (P<0.005). Separation of SS cells into four density-defined fractions by density gradient revealed mean values of Na/H EXC four to five times higher in reticulocytes (SS1), discocytes (SS2) and dense discocytes (SS3), than in the fraction containing irreversibly sickled cells and dense discocytes (SS4). In contrast to K:Cl cotransport, which dramatically decreases after reticulocyte maturation, Na/H EXC persists well after reticulocyte maturation. In density-defined, normal AA red cells, Na/H EXC decreased monotonically as cell density increased. In SS and AA red cells, the magnitude of stimulation of Na/H EXC by cell shrinkage varied from individual to individual. We conclude that Na/H EXC is highly expressed in SS and AA young red cells and decays slowly after reticulocyte maturation. 相似文献
139.
Summary The anion transport domain of the anion exchange protein (AEP) of human erythrocyte membranes (band 3, 95 kD mol wt) was probed with the substrate and affinity label pyridoxal-5-phosphate (PLP). Acting from outside, this probe labels two chymotryptic fragments of 65 and 35 kD of AEP but only the 35-kD fragment is protected from labeling by reversibly acting disulfonic stilbenes (DS). It is shown here by functional studies and by immunoblotting with anti-PLP antibodies that transmembrane gradients of anions determine the availability of a 35-kD fragmentlys residue to surface labeling by PLP, in analogy with their effects on labeling of 65-kD fragment by DS. On this basis, it is suggested that both fragments contribute to the formation of the transport domain. However, unlike DS, PLP blocks transport when reacted from within resealed membranes, indicating that the 35-kD fragment might contain components of the mobile unit of the AEP. Using impermeant fluorescence quenchers of PLP of both complexation type (anti-PLP antibodies) or collisional type (acrylamide) as topological probes for PLP-labeled sites, it is deduced that the 65-kD PLP-labeled and the 35-kD PLP-labeledlys groups are inaccessible to macromolecules from either surface, but the 65-kD PLP-lys is accessible to low molecular weight molecules from without while the 35-kD PLP-labeledlys shows accessibility primarily from within the cell surface. The studies indicate that the accommodation of a wide class of anions by AEP might be associated with the flexibility of the transport domain of the protein and its capacity to undergo transport-related conformational changes. 相似文献
140.
O. O. Olorunsogo F. O. Agbolade S. O. Owojuyigbe J. A. Adebisi A. O. Adebayo W. G. Okunade 《Bioscience reports》1990,10(3):281-291
Calpain, a calcium-dependent, neutral cysteine-protease was purified from the erythrocyte cytosol of subjects having essential hypertension (HTN), sickle cell anaemia, (SCA), or kwashiorkor (KWA). Identical electrophoretic mobility on SDS-polyacrylamide gradient gel, sensitivity to micromolar amounts of Ca2+, absolute requirement for a reducing environment and a high susceptibility to inhibition by leupeptin and thiol-group modifying reagents confirm that calpain preparations from these erythrocytes are equivalent to calpain I. Whereas the extent of calpain activation of erythrocyte membrane Ca2+-pumping ATPase of normal subjects was almost equal to that due to calmodulin, calpain activation of the HTN and SCA pump was greater than activation by calmodulin. Like in normal membranes, exogenous calmodulin protected the Ca2+-pumping ATPase of these erythrocytes against calpainization; the degree of protection by calmodulin is least in SCA and HTN. Electrophoretic separation of erythrocyte membranes and the purified Ca2+-pumping ATPase of HTN, SCA and KWA subjects does not indicate the presence of fragments resulting from the proteolytic action of calpain.Abbreviations PMSF
phenylmethylsulfonylfluoride
- TLCK
N--tosyl-L-lysine chloromethyl ketone
- EGTA
ethyleneglycol-bis (-aminoethylether) N,N1-tetraacetic acid
- ATP
adenosine 51-triphosphate
- Hepes
4-(2 hydroxyethyl)-1-piperazine ethanesulphonic acid
- Tris-HC1
Tris (hydroxymethyl) aminomethane-hydrochloride
- SDS
sodium dodecyl sulphate 相似文献