Activation of ATP hydrolysis by an uncoupler in mutant mitochondria lacking an intrinsic ATPase inhibitor in yeast

An intrinsic ATPase inhibitor and 9-kDa protein are regulatory factors of mitochondrial ATP synthase in Saccharomyces cerevisiae. A gene encoding the ATPase inhibitor was isolated from a yeast genomic library with synthetic oligonucleotides as hybridization probes and was sequenced. The deduced amino acid sequence showed that the precursor protein contains an amino-terminal presequence of 22 amino acid residues. Mutant strains that did not contain the inhibitor and/or the 9-kDa protein were constructed by transformation of cells with their in vitro disrupted genes. The disruption of the chromosomal copy in recombinant cells was verified by Southern blot analysis, and the absence of the proteins in the mutant cells was confirmed by Western blot analysis. All the mutants could grow on a nonfermentable carbon source and the oxidative phosphorylation activities of their isolated mitochondria were the same as that of normal mitochondria. However, an uncoupler, carbonylcyanide-m-chlorophenylhydrazone, induced marked ATP hydrolysis in the inhibitor-deficient mitochondria, but not in normal mitochondria. These observations suggest that the ATPase inhibitor inhibits ATP hydrolysis by F1F0-ATPase only when the membrane potential is lost.     

Translocation of colicin E1 through cytoplasmic membrane of Escherichia coli

The product of the malE—lacZ gene fusion was reported to compete with some proteins including outer membrane lipoprotein in the protein translocation across the Echerichia coli membrane. The fusion product also inhibited colicin E1 export. Furthermore, globomycin, which accumulated prolipoprotein in the membrane, inhibited the translocation of colicin E1 in the wild-type cells, but not in lipoprotein-negative mutant cells. Since colicin E1 contains the internal signal-like sequence [Proc. Natl. Acad. Sci. USA (1982) 79, 2827–2831], these results suggest that colicin E1 is exported by the aid of this sequence at a common site for maltose-binding protein and lipoprotein translocation.     

Degradation of Xyloglucan by Wall-bound Enzymes from Soybean Tissue I. Occurrence of Xyloglucan-degrading Enzymes in Soybean Cell Wall

An enzyme preparation that catalyzes the degradation of xyloglucanwas obtained by extraction of the cell walls of soybean hypocotylswith a buffer containing 1.0 M NaCl. The enzyme preparationwas shown to catalyze two-step degradation of xyloglucan. Thepolysaccharide was first degraded into comparatively large fragments,which were then further degraded into monosaccharides. In orderto elucidate the mode of degradation of the xyloglucan duringcell growth, the activities of xyloglucandegrading enzymes ofsoybean-hypocotyl segments were assayed at different stagesof elongation. The total activities of the degrading enzymeswere lower in the elongating regions than in the non-elongatingregions. However, high levels of endo-ß-l,4-glucanasewere found in the elongating regions. These results suggestthat xyloglucan is hydrolyzed by endo-ß-1,4-glucanaseinto comparatively large fragments at the initial stage of growthand the resulting fragments are further degraded into monosaccharidesduring cell elongation. (Received May 20, 1981; Accepted August 8, 1981)     

Initiation of DNA replication in Bacillus subtilis. IV. The effect of an intercalating dye, ethidium bromide

Summary The effects of an intercalating dye, ethidium bromide (EtBr), on the initiation of chromosome replication in Bacillus subtilis were studied. Spores of a thymine requiring mutant acquired the ability to initiate one round of replication in the absence of RNA and protein synthesis (initiation potential) during germination in a thymine starved medium. When EtBr was added after the initiation potential was fully established, initiation of replication was completely inhibited. This inhibition was reversible, and initiation was resumed when the drug was removed. The recovery of initiation occurred in the absence of protein synthesis but did require RNA synthesis and an active dna gene product.During germination both a DNA-protein complex and a DNA-membrane complex were formed at the replication origin in parallel with the establishment of initiation potential. EtBr destroyed both of these complexes at the concentration which inhibited initiation.The first round of replication of a plasmid DNA, pSL103, during spore germination was also prevented by EtBr. However a higher concentration was required to inhibit plasmid replication. It was found that the plasmid formed two complexes identical to the S- and M-complex of the chromosome origin. Compared to the chromosome complexes the plasmid complexes were less sensitive to EtBr. The loss of sensitivity was equivalent to that for the initiation of the plasmid compared to the chromosome. These results indicate that the target of EtBr is the DNA in the S- and M-complexes whose conformation is essential for the initiation of chromosome and plasmid replication.III of this series is Murakami et al. 1976     

Adenosine kinase from human liver

Adenosine kinase (ATP: adenosine 5'-phosphotransferase, EC 2.7.1.20) has been purified to homogeneity from human liver. The yield was 55% of the initial activity with a final specific activity of 6.3 mumol/min per mg protein. The molecular weight was estimated as about 40 000 by Sephadex G-100 gel filtration and polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS). The enzyme catalyzed the phosphorylation of adenosine, deoxyadenosine, arabinoadenosine, inosine and ribavirin. The activity of deoxyadenosine phosphorylation was 18% of that of adenosine. The pH optimum profile was biphasic; a sharp pH optimum at pH 5.5 and a broad optimum at pH 7.5--8.5. The Km value for adenosine was 0.15 micrometer, and the activity was strongly inhibited at higher concentrations than 0.5 micrometer. ATP, dATP, GTP and dGTP were proved to be effective phosphate donors. Co2+ was more effective than Mg2+, and Ca2+, Mn2+, Fe2+ and Ni2+ showed about 50% of the activity for Mg2+. Some difference in structure between the adenosine kinase from human liver and that from rabbit or rat tissue, was observed by amino acid analysis and peptide mapping analysis.     

Synthesis of D-cysteine from 3-chloro-D-alanine and hydrogen sulfide by 3-chloro-D-alanine hydrogen chloride-lyase (deaminating) of Pseudomonasputida

Synthesis of D-cysteine from 3-chloro-D-alanine and hydrogen sulfide is catalyzed by highly purified 3-chloro-D-alanine hydrogen chloride-lyase from $\text{Pseudomonas}\text{putida}$. The synthetic reaction proceeds optimally at pH 8.5, as a function of enzyme concentration and incubation time. The enzymatically synthesized D-cysteine was isolated from the large scale reaction mixture and identified by physicochemical means.     

Catalytic activity and arrangement of subunit polypeptides in rat liver cytochrome c oxidase as studied by proteolysis

Cytochrome c oxidase from rat liver was incubated with various proteinases of different specificities and the enzymic activity was measured after various incubation times. A loss of catalytic activity was found after digestion with proteinase K, aminopeptidase M and a mitochondrial proteinase from rat liver. In each case the decrease in enzymic activity was compared with the changes in intensities of the polypeptide pattern obtained after sodium dodecyl sulfate polyacrylamide gel electrophoresis. The susceptibilities of the subunit polypeptides of the soluble cytochrome c oxidase to proteinases were very different. Whereas subunit I was most susceptible, subunits V–VII were rather resistant to degradation. From the relative inaccessibility of subunits V–VII to proteinases it is likely that these polypeptides are buried in the interior of the enzyme complex.     

Circular dichroism of squid rhodopsin and its intermediates

Circular dichroism (CD) and absorption spectra of squid (Todarodes pacificus) rhodopsin, isorhodopsin and the intermediates were measured at low temperatures. Squid rhodopsin has positive CD bands at wavelengths corresponding the - and β-absorption bands at liquid nitrogen temperature (CD maxima: 485 nm at -band and 348 nm at β-band) as well as at room temperature (CD maxima: 474 nm at -band and 347 nm at β-band). The rotational strength of the -band has a molecular ellipticity about twice that of cattle rhodopsin. The CD spectrum of bathorhodopsin displays a negative peak at 532 nm, the rotational strength of which has an absolute value slightly larger than that of rhodopsin. The reversal in sign at -band of the CD spectrum may indicate that the isomerization of retinal chromophore from twisted 11-cis form to twisted 11-trans form has occurred in the process of conversion from rhodopsin to bathorhodopsin. Lumirhodopsin has a small negative CD band at 490 nm, the maximum of which lies at 25 nm shorter wavelengths than the absorption maximum (515 nm), and a large positive CD band near 290 nm, which is not observed in rhodopsin and the other intermediates. This band may be derived from a conformational change of the opsin. In the process of changing from lumirhodopsin to LM-rhodopsin, the CD bands at visible and near ultraviolet regions disappear. Both alkaline and acid metarhodopsins have no CD bands at visible and near ultraviolet regions.     

Distribution of AMP-deaminase isozymes in rat tissues

1. The distribution of AMP deaminase isozymes in rat tissues was analyzed by electrophoresis on cellulose acetate membrane, by chromatography on phosphocellulose column, and by the application of immunological technique employing specific antisera against three parental AMP deaminases (isozymes A, B and C). Skeletal muscle extracts and diaphragm extracts contain a single identical isozyme, isozyme A. The major isozyme species of liver, kidney and testes are also identical and they are isozyme B. Heart extracts contains isozyme C exclusively. Extracts of brain, lung and spleen contain five isozymes, presumably a complete set of five B-C hybrids. 2. Developmental patterns of AMP deaminase isozyme were studied. In early postnatal life, extracts of heart, liver, kidney and lung contain five isozymes similar to those observed in adult brain. During postnatal development, a shift to isozyme C occurs in heart, whereas a shift to isozyme B occurs in liver and kidney. Five isozymes in lung remain throughout development. In brain a shift of B to five isozymes is observed during development. Isozyme A is the predominant form in muscle throughout postnatal development. 3. AMP deaminase in the regenerating liver was analyzed, but the data indicated that there was no change of isozyme distribution during hepatic regeneration.     

Gibberellic acid-induced secretion of hydrolases in barley aleurone layers

Activities of phosphatases in the aleurone layers of a husklessbarley, Ehime-hadaka No. 1, were enhanced in the absence ofgibberellic acid (GA₃), while the enzyme secretion was absolutelydependent upon its presence. GA₃ was required for both inductionand secretion of a-amylase. The longer the preincubation ofthe tissue without GA₃, the longer was the lag period beforesecretion of both a group of phosphatases and a-amylase. Changesin the fine structure of aleurone cells were also investigated.Characteristics of the phase transition from enzyme accumulationto enzyme secretion seemed to be a development of a bundledtype of endoplasmic reticulum. ¹Present address: Institute of Biological Sciences, The Universityof Tsukuba, Ibaraki 300-31, Japan. (Received August 25, 1975; )