Characterization of a genomic and cDNA clone coding for the thioesterase domain and 3' noncoding region of the chicken liver fatty acid synthase gene

The fatty acid synthase (FAS) of animal tissue is a dimer of two identical subunits, each with a Mr of 260,000. The subunit is a single multifunctional protein having seven catalytic activities and a site for binding of the prosthetic group 4'-phosphopantetheine. The mRNA coding for the subunit has an estimated size of 10-16 kb, which is about twice the number of nucleotides needed to code for the estimated 2300 amino acids. We have isolated a positive clone, lambda CFAS, containing FAS gene sequences by screening a chicken genomic library with a segment of a 3' untranslated region of goose fatty acid synthase cDNA clone, pGFAS3, as a hybridization probe. The DNA insert in lambda CFAS hybridizes with synthetic oligonucleotide probes prepared according to the known amino acid sequence of the thioesterase component of the chicken liver fatty acid synthase [Yang, C.-Y., Huang, W.-Y., Chirala, S., & Wakil, S.J. (1988) Biochemistry (preceding paper in this issue)]. Further characterization of the DNA insert shows that the lambda CFAS clone contains about a 4.7-kbp segment from the 3' end of the chicken FAS gene that codes for a portion of the thioesterase domain. Complete sequence analyses of this segment including S1 nuclease mapping, showed that the lambda CFAS clone contains the entire 3' untranslated region of the chicken FAS gene and three exons that code for 162 amino acids of the thioesterase domain from the COOH-terminal end of the fatty acid synthase. Using the exon region of the genomic clone, we were able to isolate a cDNA clone that codes for the entire thioesterase domain of chicken liver fatty acid synthase.(ABSTRACT TRUNCATED AT 250 WORDS)     

The topography of glycerophosphate acyltransferase in the transverse plane of the mitochondrial outer membrane

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.     

The site of synthesis of mitochondrial proteins in Krebs II ascites-tumour cells

At 22° in Earle's medium, Krebs cells synthesize proteins. After a brief `pulse' with [<sup>14</sup>C]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.     

Trypsin inhibitors from ridged gourd (Luffa acutangula Linn.) seeds: Purification, properties, and amino acid sequences

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.     

Evaluation of anti-inflammatory activity of Vernonia cinerea Less. extract in rats.

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.).     

Trypsin inhibitors from ridged gourd (Luffa acutangula Linn.) seeds: Purification,properties, and amino acid sequences

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.     

Simultaneous reconstitution of Escherichia coli membrane vesicles with D-lactate and D-amino acid dehydrogenases

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.     

A simple method of characterizing mitochondrial ribonucleic acid.

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.