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1.
The topography of glycerophosphate acyltransferase in the transverse plane of the mitochondrial outer membrane 总被引:2,自引:0,他引:2
In low ionic media, mitochondrial glycerophosphate acyltransferase was inhibited virtually completely within 15 min by the nonspecific proteases, proteinase K and subtilisin. In high ionic media, the mitochondrial enzyme was either not inhibited or was marginally inhibited by these proteases. Chymotrypsin and trypsin, regardless of the ionic strength of the medium, did not inhibit the acyltransferase. Substantial inhibition by proteinase K and subtilisin was observed in the high ionic media when the incubation was continued for 30 or 45 min. Adenylate kinase, an intermembrane enzyme, was not inhibited under any of the above conditions. These results demonstrate a cytosolic exposure of the mitochondrial acyltransferase. In a low ionic environment, when the outer membrane integrity was damaged either by gradually decreasing the tonicity of the medium or by stepwise addition of Triton X-100, either chymotrypsin or trypsin caused virtually parallel inhibition of glycerophosphate acyltransferase and adenylate kinase. A more direct approach in establishing the existence of protease-susceptible sites on the inner side of the outer membrane was taken by observing the inhibition of mitochondrial glycerophosphate acyltransferase and adenylate kinase in trypsinloaded right-side-out outer membrane vesicles incubated in the presence of externally located soybean trypsin inhibitor. The above results, taken together, suggest that mitochondrial glycerophosphate acyltransferase spans the transverse plane of the outer membrane. 相似文献
2.
The site of synthesis of mitochondrial proteins in Krebs II ascites-tumour cells 总被引:5,自引:3,他引:2 下载免费PDF全文
At 22° in Earle's medium, Krebs cells synthesize proteins. After a brief `pulse' with [14C]valine followed by a `chase' of [12C]valine the radioactivity appears first in microsomes and is transferred after `chase' to the cell sap. Kinetics of labelling of the mitochondrial protein are different from that of either microsomal or cell-sap protein. When Krebs cells in buffer are mixed with ribonuclease in water the nuclease penetrates the cell membrane. The ribonuclease-treated cells are still viable but have lost most of their cytoplasmic ribosomes (electron micrograph). Such cells still synthesize mitochondrial protein at near normal rate but synthesis of microsomal protein is severely inhibited. The results indicate that some mitochondrial proteins are synthesized independently of the microsome–cell-sap system. 相似文献
3.
Umesh C. Haldar Sanat K. Saha Ronald C. Beavis Nirmal K. Sinha 《Journal of Protein Chemistry》1996,15(2):177-184
Two trypsin inhibitors, LA-1 and LA-2, have been isolated from ridged gourd (Luffa acutangula Linn.) seeds and purified to homogeneity by gel filtration followed by ion-exchange chromatography. The isoelectric point is atpH 4.55 for LA-1 and atpH 5.85 for LA-2. The Stokes radius of each inhibitor is 11.4 å. The fluorescence emission spectrum of each inhibitor is similar to that of the free tyrosine. The biomolecular rate constant of acrylamide quenching is 1.0×109 M–1 sec–1 for LA-1 and 0.8 × 109 M–1 sec–1 for LA-2 and that of K2HPO4 quenching is 1.6×1011 M–1 sec–1 for LA-1 and 1.2×1011M–1 sec–1 for LA-2. Analysis of the circular dichroic spectra yields 40%-helix and 60%-turn for La-1 and 45%-helix and 55%-turn for LA-2. Inhibitors LA-1 and LA-2 consist of 28 and 29 amino acid residues, respectively. They lack threonine, alanine, valine, and tryptophan. Both inhibitors strongly inhibit trypsin by forming enzymeinhibitor complexes at a molar ratio of unity. A chemical modification study suggests the involvement of arginine of LA-1 and lysine of LA-2 in their reactive sites. The inhibitors are very similar in their amino acid sequences, and show sequence homology with other squash family inhibitors. 相似文献
4.
5.
U K Mazumder M Gupta L Manikandan S Bhattacharya P K Haldar S Roy 《Phytomedicine》2003,10(2-3):185-188
The methanol extract of the whole plant of Vernonia cinerea Less. was evaluated for its anti-inflammatory activity in acute (carrageenin, histamine and serotonin induced rat paw edema) and a chronic model (cotton pouch induced granuloma). The methanol extract (250 and 500 mg/kg(-1) p.o.) exhibited significant activity (p < 0.001) against all phlogistic agents used in a dose dependant manner. In the chronic model (cotton pouch granuloma method) the methanol extract exhibited significant anti-inflammatory activity. All these effects were compared with standard drug phenylbutazone (100 mg/kg(-1) p.o.). 相似文献
6.
Umesh C. Haldar Sanat K. Saha Ronald C. Beavis Nirmal K. Sinha 《The protein journal》1996,15(2):177-184
Two trypsin inhibitors, LA-1 and LA-2, have been isolated from ridged gourd (Luffa acutangula Linn.) seeds and purified to homogeneity by gel filtration followed by ion-exchange chromatography. The isoelectric point is atpH 4.55 for LA-1 and atpH 5.85 for LA-2. The Stokes radius of each inhibitor is 11.4 å. The fluorescence emission spectrum of each inhibitor is similar to that of the free tyrosine. The biomolecular rate constant of acrylamide quenching is 1.0×109 M?1 sec?1 for LA-1 and 0.8 × 109 M?1 sec?1 for LA-2 and that of K2HPO4 quenching is 1.6×1011 M?1 sec?1 for LA-1 and 1.2×1011M?1 sec?1 for LA-2. Analysis of the circular dichroic spectra yields 40%α-helix and 60%Β-turn for La-1 and 45%α-helix and 55%Β-turn for LA-2. Inhibitors LA-1 and LA-2 consist of 28 and 29 amino acid residues, respectively. They lack threonine, alanine, valine, and tryptophan. Both inhibitors strongly inhibit trypsin by forming enzymeinhibitor complexes at a molar ratio of unity. A chemical modification study suggests the involvement of arginine of LA-1 and lysine of LA-2 in their reactive sites. The inhibitors are very similar in their amino acid sequences, and show sequence homology with other squash family inhibitors. 相似文献
7.
Mausumi Mutsuddi Debasish Mutsuddi A. S. Mukherjee Ashish K. Duttagupta 《Chromosoma》1984,89(1):55-62
The chromosome complement of hybrid males from the cross between Drosophila miranda female and D. persimilis male provides an interesting chromosomal situation where an autosome, the 3rd chromosome of D. persimilis, coexists with a homologue that developed into a sex chromosome, the X2 in D. miranda. Except for certain inversions and a few minor translocations, these two chromosomes (X2 and the 3rd) still look alike as polytene elements. However, in hybrid males pairing of the two chromosomes, the X2 and 3rd, is rare, while in female hybrids it occurs frequently. — 3H-TdR labeling shows that while the X2 and 3rd chromosomes replicate synchronously in hybrid female, in the hybrid male the former completes its replication earlier than the 3rd chromosome, as do the two arms of the X1 (XL and XR). The frequency and relative intensity of 3H-TdR labeling of each site of the X2 and that of the 3rd chromosome in hybrid males closely agree with those of the corresponding sites in the X2 of the miranda male and the 3rd chromosome of the persimilis male (or female), respectively. The results suggest that timing and rate of replication of the X2 are determined autonomously and follow the pattern in the respective parental species. 相似文献
8.
9.
Simultaneous reconstitution of Escherichia coli membrane vesicles with D-lactate and D-amino acid dehydrogenases 总被引:2,自引:0,他引:2
K Haldar P J Olsiewski C Walsh G J Kaczorowski A Bhaduri H R Kaback 《Biochemistry》1982,21(19):4590-4596
Purified preparations of D-amino acid dehydrogenase [Olsiewski, P.J., Kaczorowski, G. J., & Walsh, C. T. (1980) J. Biol. Chem. 225, 4487] and D-lactate dehydrogenase [Kohn, L.D., & Kaback, H.R. (1973) J. Biol. Chem. 248, 7012] bind independently to right-side-out and inverted Escherichia coli vesicles and to phosphatidylcholine liposomes without detectable competition. The reconstituted vesicles catalyze D-lactate- and D-alanine-dependent respiration (O2 uptake), proton translocation, and proton/lactose symport. The enzymes do not share common sites of association on either face of the E. coli membrane, and binding of both enzymes to the bilayer appears to be due to nonspecific affinity for the surface rather than specific binding to proteinaceous receptors. Each enzyme, however, appears to reduce a common proton translocating step in the membrane-bound respiratory chain, and substrate-derived electrons are transferred through a common rate-determining redox component that precedes the site of proton translocation. The results suggest that although binding is nonspecific, there is a common site for proton translocation in the membrane between the flavin-linked dehydrogenases and the cytochromes and that this site is accessible by distinct routes of electron transfer from primary dehydrogenases on either surface of the membrane. 相似文献
10.
A simple method of isolating and characterizing RNA from L-cell mitochondria is described. The mitochondrial fraction is lysed by sodium dodecyl sulphate, and the RNA fractionated by sucrose-density-gradient centrifugation. The efficacy of proteinase K in preventing ribonuclease activity is also demonstrated. 相似文献