Biomedical subjects

F Y Yang

Publications and source records attributed to F Y Yang.

At least 37 records · Page 2Linked to original sources

PubMed1996

Se-mediated domain-domain communication in band 3 of human erythrocytes.

Na2SeO3 could affect the anion flux of Band 3 of inside-out erythrocyte membrane vesicles (IOVs). Such effect was believed to be based on the interaction of SH groups of Band 3 with Na2SeO3. This effect could be eliminated when the cytoplasmic domain of Band 3 was proteolytically removed by trypsin. This suggested that SH groups in the cytoplasmic domain were involved in such interaction. Measurement of the pH dependence of intrinsic fluorescence intensity provided evidence that conformational changes of Band 3 occurred as a consequence of interaction with selenite. KI quenching of intrinsic fluorescence of Band 3 could also show that there was a conformational change in the cytoplasmic domain of Band 3 after reaction with Na2SeO3. Such conformational change in turn could be transmitted to the membrane domain of Band 3 monitored by quenching of intrinsic fluorescence of Band 3 using hypocrellin B (HB) (a photosensitive pigment obtained from a parasitic fungus growing in Yunnan, China). It is suggested that the cytoplasmic domain of Band 3 is not necessary for its anion flux, but is essential for the regulation (e.g., by Se) of its active site located at the membrane domain, and hence, it may provide evidence of communication between the cytoplasmic domain and the membrane domain of Band 3.

Anion Exchange Protein 1, Erythrocyte↗

PubMed1995

Effect of propensity of hexagonal II phase formation on the activity of mitochondrial ubiquinol-cytochrome c reductase and H(+)-ATPase.

The propensity of hexagonal II phase formation plays an important role in the activity of mitochondrial ubiquinol-cytochrome c reductase or H(+)-ATPase. The respiratory control ratio of reconstituted ubiquinol-cytochrome c reductase or the ATP-induced membrane potential of reconstituted H(+)-ATPase became higher as the non-bilayer phospholipid phosphatidylethanolamine content of proteoliposomes increased. The highest respiratory control ratio or ATP-induced membrane potential was obtained in the case of 60-80% phosphatidylethanolamine-containing proteoliposomes. Dioleoylphosphatidylethanolamine could significantly enhance the respiratory control ratio of ubiquinol-cytochrome c reductase and ATP-induced membrane potential of H(+)-ATPase, while no obvious change could be observed when dielaidoylphosphatidylethanolamine was used. The bilayer to hexagonal II phase transition temperature of ubiquinol-cytochrome c reductase-containing proteoliposomes reconstituted with phosphatidylcholine+phosphatidylethanolamine increases with decreasing content of phosphatidylethanolamine. Several additives such as the bilayer stabilizers, cholesterol 3-sulfate and carbobenzoxy-D-Phe-L-PheGly, or hexagonal II phase-forming promoters, such as diolein or eicosane, can decrease or increase the activity of these two enzyme complexes.

Adenosine Triphosphate↗

PubMed1995

Effect of transmembrane Ca2+ gradient on Gs function.

Gs and adenylate cyclase from bovine brain cortices were co-reconstituted into asolectin liposomes with or without 1000-fold transmembrane Ca2+ gradient. Obtained results showed that Gs activities of both binding GTP gamma S and stimulating adenylate cyclase were the highest in proteoliposomes, with a transmembrane Ca2+ gradient similar to the physiological situation and the lowest while the transmembrane Ca2+ gradient was in the inverse direction. Such a difference could be diminished following the dissipation of the transmembrane Ca2+ gradient by A23187. Time-resolved fluorescence anisotropy of diphenylhexatriene (DPH) has been used to compare the physical state of phospholipids among those proteoliposomes. It is suggested that a proper transmembrane Ca2+ gradient is essential for higher membrane fluidity, which may favor Gs function with higher GTP-binding activity and stimulation of adenylate cyclase.

Adenylyl Cyclases↗

PubMed1995

Transmembrane Ca2+ gradient and function of membrane proteins.

This review will focus on the recent advance in the study of effect of transmembrane Ca2+ gradient on the function of membrane proteins. It consits of two parts: 1. Transmembrane Ca2+ gradient and sarcoplasmic reticulum Ca(2+)-ATPase; 2. Effect of transmembrane Ca2+ gradient on the components and coupling of cAMP signal transduction pathway. The results obtained indicate that a proper transmembrane Ca2+ gradient may play an important role in modulating the conformation and activity of SR Ca(2+)-ATPase and the function of membrane proteins involved in the cAMP signal transduction by mediating the physical state change of the membrane phospholipids.

Animals↗

PubMed1995

Zn(2+)-mediated domain-domain communication in human erythrocyte band 3.

Zn2+ could inhibit the anion transport activity of spectrin-stripped inside-out human erythrocyte membrane vesicles (IOVs). Removal of the cytoplasmic domain from Band 3 by trypsin could eliminate Zn2+ inhibition. The location of a Zn(2+)-binding site was confirmed by atomic absorbance spectrometry. The results of time-resolved fluorescence and intrinsic fluorescence quenching by KI and hypocrellin B (a photosensitive pigment obtained from a parasitic fungus growing in Yunnan, China) showed that the cytoplasmic domain is necessary for the Zn(2+)-induced conformational changes of the whole molecule as well as the membrane domain of Band 3. It is suggested that Zn2+ induced a conformational change in the cytoplasmic domain of Band 3, which in turn was transmitted to the membrane domain, resulting in an inhibition of activity of Band 3. Such long-range conformational changes may imply that the cytoplasmic domain is poised to function as a cytosolic arm in order to modulate the structure of the membrane domain of Band 3.

Anion Exchange Protein 1, Erythrocyte↗

PubMed1995

Cytoplasmic Ca2+ inhibits the glucose transporter of human erythrocytes.

The effect of Ca2+ on the glucose transporter of human erythrocytes was investigated. The results showed that extracellular Ca2+ had no effect. But, the glucose transport of erythrocytes was markedly inhibited due to the increase in cytoplasmic Ca2+ concentration by addition of ionophore A23187. The Ca2+ inhibition exhibited a dose-dependent manner with an apparent half maximal concentration of 250 microM and could not be recovered by 10 mM EGTA. Unlike Ca2+, Mg2+ did not affect the glucose transporter.

Calcimycin↗

PubMed1995

Hydrophobic interaction and folding propensity of chicken heart apocytochrome c.

In contrast to horse heart apocytochrome c, the chicken one showed quite different folding propensity as titrated by NaCl at different pH. At pH 2.0, folding behaviour of both apocytochrome c are essentially similar; while at pH higher than 4.0, chicken heart apocytochrome c has much enhanced propensity to fold and aggregate, as was shown by circular dichroism spectra, intrinsic fluorescence and non-denatured polyacrylamide gel electrophoresis. Hydrophobic chromatography demonstrated much higher hydrophobicity of chicken heart apocytochrome c, thus strongly suggested that it is the hydrophobic interaction that stabilize the 'Molten Globule' like, partially-folded structure of chicken heart apocytochrome c at neutral pH.

Animals↗

PubMed1995

Cloning and high-level expression of chicken apocytochrome c gene in Escherichia coli.

Chicken apocytochrome c gene with correct reading frame was easily cloned through excision by polymerase chain reaction of the intron in the genomic clone of chicken cytochrome c gene, and was successfully overexpressed in Escherichia coli by cloning into expression vector pET-3d under the control of T7 promoter. Expressed protein can amount to as high as 40% of the total protein and mainly presents as inclusion body. Purification of chicken apocytochrome c from the inclusion body and characterization by SDS-PAGE, isoelectric focusing electrophoresis, and amino acid analysis showed that the purified apocytochrome c is identical to that prepared from chicken heart cytochrome c by chemically depletion of heme.

Animals↗

PubMed1994

Fluorescence study on transmembrane Ca2+ gradient-mediated conformation changes of sarcoplasmic reticulum Ca(2+)-ATPase.

The conformational states of Ca(2+)-ATPase in sarcoplasmic reticulum (SR) vesicles with or without a thousand-fold transmembrane Ca2+ gradient have been studied by fluorescence spectroscopy and fluorescence quenching. In consequence of the establishment of the transmembrane Ca2+ gradient, the steady-state fluorescence results revealed a reproducible 8% decrease in the intrinsic fluorescence while time-resolved fluorescence measurements showed that 13 tryptophan residues in SR.Ca(2+)-ATPase could be divided into three groups. The fluorescence lifetime of one of these groups increased from 5.5 ns to 5.95 ns in the presence of a Ca2+ gradient. Using KI and hypocrellin B (a photosensitive pigment obtained from a parasitic fungus, growing in Yunnan, China), the fluorescence quenching further indicated that the dynamic change of this tryptophan group, located at the protein-lipid interface, is a characteristic of transmembrane Ca2+ gradient-mediated conformational changes in SR.Ca(2+)-ATPase.

Animals↗

PubMed1994

Correlation between unfolded states of apocytochrome c and its ability to pass lipid bilayer.

In contrast to the horse heart apocytochrome c, the chicken heart apocytochrome c underwent a conformational change from random coil to partial folding during a renaturation process. When the apocytochrome horse heart and that of chicken heart c were subjected to a translocation assay in vitro using large trypsin-enclosed unilamellar vesicles from soybean phospholipids, the ability of the chicken heart apocytochrome c to penetrate into the liposomes was found to decrease markedly with the renaturation procedure, while that of horse heart apocytochrome c remained relatively constant. Observations from circular dichroism measurement on the induction of secondary folding of these two species of apocytochrome c upon interaction with soybean phospholipid vesicles suggested that a more flexible structure of apocytochrome c embedded in the lipid matrix be required for its efficient translocation across the bilayer.

Amino Acid Sequence↗

PubMed1994

Transmembrane Ca2+ gradient-mediated change of fluidity in the inner layer of phospholipids modulates Ca(2+)-ATPase of sarcoplasmic reticulum.

Sarcoplasmic reticulum (SR) vesicles with (1000 folds) or without transmembrane Ca2+ gradient have been prepared. Different fluorescence probes (DPH, TMA-DPH and n-AS), were used to determine the effect of transmembrane Ca2+ gradient on the lipid fluidity both in outer and inner layer of Ca(2+)-ATPase-containing SR vesicles. The results showed that transmembrane Ca2+ gradient could significantly decrease the fluidity of the inner layer of SR membrane, while no obvious change was monitored in the outer layer. This may be deduced that Ca(2+)-ATPase might be modulated mainly by the transmembrane Ca2+ gradient-mediated alteration of physical state of phospholipid in the inner layer of SR membrane.

Animals↗

PubMed1993

Transmembrane Ca2+ gradient-mediated modulation of sarcoplasmic reticulum Ca(2+)-ATPase.

Ca(2+)-ATPase from skeletal muscle sarcoplasmic reticulum was reconstituted into liposomes with (100-1000 fold) or without transmembrane Ca2+ gradient. The highest enzyme activity and Ca2+ uptake were observed in the vesicles without transmembrane Ca2+ gradient. If there existed transmembrane Ca2+ gradient, no matter what the direction was, a lower activity would appear. Dissipation of transmembrane Ca2+ gradient by A23187 could lead to a change in enzyme activity of incorporated Ca(2+)-ATPase. A concomitant change of lipid fluidity of proteoliposomes with that of enzyme activity and Ca2+ uptake was observed. The inhibition of Ca(2+)-ATPase by the transmembrane Ca2+ gradient could be observed in the PC-PE vesicles, but not in the PS-PE or PG-PE proteoliposomes.

Adenosine Triphosphate↗

PubMed1993

Divalent cation and lipid-protein interactions of biomembranes.

Divalent cations play an important role in the functions of biomembranes. This review deals with three topics: (1) Mg(2+)-mediated change in physical state of phospholipid induces conformation and activity change of reconstituted mitochondrial H(+)-ATPase, (2) a proper transmembrane Ca2+ gradient is essential for the higher enzymatic activity of adenylate cyclase, and (3) role of transmembrane Ca2+ gradient in the modulation of reconstituted sarcoplasmic reticulum Ca(2+)-ATPase activity.

Animals↗

PubMed1993

[The specificity of modulation of sarcoplasmic reticulum Ca(2+)-ATPase by transmembrane Ca2+ gradient].

We have previously reported that transmembrane Ca2+ gradient-mediated changes in lipid fluidity could modulate the conformation and enzyme activity of sarcoplasmic reticulum (SR) Ca(2+)-ATPase. The aim of this paper is to explore the specificity of transmembrane Ca2+ gradient-mediated modulation of SR Ca(2+)-ATPase. The results showed that such specificity exhibited in two aspects: 1. The modulation could not be ascribed to transmembrane potential resulted from the transmembrane Ca2+ gradient, Dissipation of transmembrane potential by FCCP (carbonylcyanide-p-trifluoromethoxyphenylhydrazone) could not affect the activity of SR Ca(2+)-ATPase. 2. Transmembrane Sr2+ gradient had little effect on the enzyme activity of SR Ca(2+)-ATPase. A significant difference between the effect of transmembrane Ca2+ and Sr2+ gradient on the lipid fluidity was detected in the middle region of bilayer of Ca(2+)-ATPase incorporated proteoliposomes using a set of n-AS [n-(9-anthroyloxy) fatty acids] fluorescence polarization probes. It is known that Ca2+ binding domain of SR Ca(2+)-ATPase is just located in the middle region of bilayer, hence it may be deduced that possibly, membrane lipids are involved in transmembrane Ca2+ gradient-mediated modulation of Ca(2+)-ATPase.

Animals↗

PubMed1993

Study on the translocation of chicken heart apocytochrome C with different unfolded states.

Chemically-prepared chicken heart apocytochrome c with different unfolded states could be obtained during the renaturation process. They exhibited distinct circular dichroism patterns designated as Apo C1 (random coiled), Apo C2 (less ordered) and Apo C3 (more ordered). This characteristic is unique to chicken heart apocytochrome c while compared with its counterparts from Candida krusei, tuna heart or horse heart and promises the emergence of much more detail of correlation of translocation with unfolded states of apocytochrome c. When chicken heart apocytochrome c was subjected to a translocation assay in vitro using trypsin-enclosed large unilamellar vesicles from soybean phospholipids, the ability of the protein to penetrate into the liposomes was found to follow the order of Apo C1 > Apo C2 > Apo C3. Conformational alterations of Apo C1, Apo C2 and Apo C3 in association with soybean phospholipid vesicles shown by circular dichroism measurement demonstrated that Apo C1 bound to phospholipids existed in a more loosely folded conformation than Apo C2 and Apo C3. We propose that a more flexible structure of apocytochrome c following the interaction with phospholipids is required for its efficient translocation across the bilayer.

Animals↗

PubMed1993

The ability of apocytochrome C to pass lipid bilayer is relevant with its folding state.

The translocation ability of two different species of apocytochrome c(horse heart, Candida krusei) across the soybean phospholipid vesicles decreased in the order: C. krusei > horse heart. Theoretical calculations of the amphiphilicity of their N- and C-terminal alpha-helix formation and the release experiment using calcein-enclosed soybean phospholipid vesicles showed that there was no direct relevance between their import ratio and the amphiphilic helicity. On the other hand, taking the advantage of circular dichroism technique, a more loosely folded structure of C. krusei following the interaction with soybean phospholipid vesicles was observed which should be responsible for the difference in translocation rate.

Animals↗

PubMed1992

Study of the lipid-protein interaction of F ATPases.

Mg2+ may play a role in altering the lipid fluidity of the bilayers which would induce a change in conformation of the F0 portion of the H(+)-ATPase complex. This change could be transmitted to the soluble F1 portion, the conformation of which is in turn altered, resulting in higher enzymic activity. In addition to mitochondrial H(+)-ATPase, similar Mg2+ effects on the reconstitution of chloroplast H(+)-ATPase and other intrinsic membrane proteins have also been observed in our laboratory.

Animals↗

PubMed1992

The effect of selenium on the function of the anion transporter (Band 3) of erythrocyte membranes.

The transport activity of Band 3 of spectrin-stripped inside-out erythrocyte membrane vesicles (IOVs) or resealed ghosts was enhanced in the presence of trace amounts of Na2SeO3 (0.2-0.5 p.p.m.); however, at higher concentrations of Na2SeO3 (> 4.0 p.p.m.), an inverse result was obtained. Reassociation of spectrin with IOVs has no effect either on the transport activity of Band 3 or on the enhancement of its activity by Na2SeO3. Sulfhydryl reagents (p-chloromercuribenzoic acid and N-ethylmaleimide) could also inhibit Band 3 activity and eliminate the selenium effect. It is suggested that SH groups are involved in anion transport of Band 3 and that the selenium effect is based on the interaction of SH groups of Band 3 with Na2SeO3.

Anion Exchange Protein 1, Erythrocyte↗