PubMed Health⌕ Search

Biomedical subjects

F Lederer

Publications and source records attributed to F Lederer.

At least 145 records · Page 8Linked to original sources
PubMed1979

Comparison of amino acid compositions of mitochondrial and cytoplasmic ribosomal proteins of Saccharomyces cerevisiae.

The amino-acid compositions of the mitochondrial ribosomal subunits of Saccharomyces cerevisiae have been determined and compared to those of cytoplasmic ribosomal subunits. For the large subunits, the mitochondrial and cytoplasmic ribosomes showed major differences in the proportions of arginine, alanine and methionine. For the small subunits, arginine, aspartic acid, alanine, valine and methionine showed marked differences. We have compared these amino-acid compositions with those already published of bacterial and eukaryotic ribosomes by a statistical method of data analysis. It appeared clearly that the yeast mitoribosomes are more distant from bacterial ribosomes than from eukaryotic cytoribosomes.

Amino Acids↗
PubMed1979

Methylated amino acids in ribosomal proteins from Escherichia coli treated with ethionine and from a mutant lacking methylation of protein L11.

In the present study, the nature, proportions and distribution of methylated amino acids in ribosomal proteins from Escherichia coli grown in the presence of ethionine and from mutant prm 1 were studied. The undermethylated ribosomes had been labeled by addition in vitro or in vivo of radioactive methyl groups from S-adenosylmethionine or from methionine. The following compounds were identified : N alpha-mono-, di- and trimethylalanines, N epsilon-mono-, di- and trimethyllysines, methylamine and N alpha-trimethylalanyllysine. Except for the latter compound and N-alpha-dimethylalanine, all other derivatives had been previously identified in the literature. It is shown that the dipeptide had been in the past mistaken for N epsilon-monomethyllysine, and arises through incomplete hydrolysis in 24 hrs of the N-terminal peptide bond of protein L11. The results of the present study are discussed in the light of previous work on ribosomal protein methylation by the authors and other workers in the field.

Alanine↗
PubMed1978

Binding of Cibacron Blue F3GA to flavocytochrome b2 from baker's yeast.

1. Flavin-free cytochrome b2 has been prepared by rapid Sephadex filtration at acid pH. The method, which yields an apo-enzyme with high reconstitution potential and has several advantages over previously used procedures, is described in detail. 2. Flavin-free cytochrome b2 thus prepared is retained by blue-dextran-bound Sepharose. It can be eluted by an increase in ionic strength, by dilute ethylene glycol and specifically by low concentrations of FMN. The holoenzyme is not retarded at all. 3. Both flavin-free and holocytochrome b2 bind Cibacron blue F3GA with appearance of distinct difference spectra. Cibacron blue is an inhibitor for the holoenzyme, it shows mixed type inhibition with respect to lactate. 4. It is concluded that there are two types of binding sites for Cibacron blue F3GA on flavocytochrome b2. Both possess ionic and hydrophobic character; one of them, which is the flavin binding site, is only available in the absence of the cofactor. Taken together these results may mean that the enzyme possesses a local flavin-binding structure similar to the 'dinucleotide fold'.

Anthracenes↗
PubMed1978

Surface differences and similarities in two homologous proteins. Cytochrome b5 and cytochrome b2 core.

From previous work (Guiard, B., Groudinsky, O. and Lederer, F. (1974) Proc. Natl. Acad. Sci. U.S. 71, 2539-2543) it is now clear that the overall secondary and tertiary structure of cytochrome b2 core is very similar to that of cytochrome b5. We present here a direct comparison of circular dichroism spectra and low-temperature absorption spectra which bring further evidence about this structural similarity. Cytochrome b2 core reacts only sluggishly with cytochrome b5 reductase, showing a lack of correspondence with the reductase binding area in cytochrome b5. On the other hand, literature data indicate similar electron transfer rates between cytochrome c on one hand, cytochrome b5 and cytochrome b2 core on the other hand. A structural inspection of cytochrome b2 core suggests that the mouth of the heme crevice in the latter is the most likely region for interaction with cytochrome c, with perhaps ionic bonds slightly different from those proposed by Salemme (Salemme, F.R. (1976) J. Mol. Biol. 102, 563--568) for the cytochrome c-cytochrome b5 interaction. In view of this partial surface similarity, the lack of immunological cross-reactivity between the two hemoprotein cores is attributed to their close similarity with the cytochrome b5 of the antibody-producing rabbit.

Animals↗
PubMed1978

Sulfite binding to a flavodehydrogenase, cytochrome b2 from baker's yeast.

Baker's yeast L-lactate dehydrogenase (flavocytochrome b2) is a typical flavodehydrogenase, in that it accepts two electrons from the substrate but has a monoelectronic acceptor. Yet it forms a red semiquinone [Capeillère Blandin et al. Eur. J. Biochem. 54, 549--566 (1975)] and it is shown in this paper that it forms a reversible covalent complex with sulfite (Kd = 1.4 muM). This complex can be observed by difference spectroscopy and provides a convenient tool for visualizing the flavin chromophore, usually hidden behind the intense heme absorbance. A number of anions (D-lactate, oxalate and pyruvate) are inhibitors of the enzymatic reaction and induce spectral perturbations of the flavin spectrum. It is concluded that probably two positive charges exist at the active site: one which stabilizes the red semiquinone and one which attracts organic anions and sulfite. It is also concluded that the correlation between reactivity with sulfite and reactivity with oxygen among flavo-proteins may not be as general as previously proposed [Massey et al. J. Biol. Chem. 244, 3999--4006 (1969)].

Circular Dichroism↗
PubMed1978

Cytochrome c from Schizosaccharomyces pombe. 2. Amino-acid sequence.

The amino acid sequence of Schizosaccharomyces pombe cytochrome c has been established by automatic degradation of the protein and by manual degradation of fragments obtained by cyanogen bromide cleavage and chymotryptic digestion. The chymotryptic peptides were aligned by homology with other known cytochrome c sequences. The protein is 108 residues long, with a four-residue amino-terminal tail. It has only one methionine residue and differs from other fungal cytochromes c in lacking the one-residue deletion at the C-terminal end. After a cyanogen bromide step, an unexpected cleavage of the peptide chain before a cysteine residue was observed. This is ascribed to formation of a dehydroalanyl residue during an incomplete S-carboxymethylation of the apoprotein, and subsequent cleavage under acidic conditions. Experimental evidence is presented in favour of the proposed mechanisms.

Amino Acid Sequence↗
PubMed1977

The "b5-like" domain from chicken-liver sulfite oxidase: a new case of common ancestral origin with liver cytochrome b5 and bakers' yeast cytochrome b2 core.

Limited chymotryptic digestion of chicken-liver sulfite oxidase destroys its ability to oxidize sulfite. From the digest can be isolated a heme-binding fragment of molecular weight about 11 000. Its purification is described, as well as its characterization by a number of methods (absorption spectroscopy, circular dichroism, electrophoretic mobility, immunochemical reactivity, amino acid analysis). The heme spectrum shows no detectable difference with that of the native enzyme. The N-terminal sequence of this sulfite oxidase core is reported (34 residues). It shows a strong similarity to that of liver microsomal cytochrome b5 and bakers' yeast cytochrome b2 core. The sequence comparison is discussed in terms of structural similarity to cytochrome b5. Our data suggest a common evolutionary origin for the three b-type cytochromes.

Amino Acid Sequence↗
PubMed1977

Bromopyruvate as an affinity label for baker's yeast flavocytochrome b2. Kinetic study of the inactivation reaction.

Bromopyruvate was shown to completely inactivate cytochrome b2 in a reaction that obeyed the kinetic criteria required for affinity labels: it inactivated flavocytochrome b2 according to saturation kinetics, and the inactivation reaction was competitively inhibited by the substrate or competitive inhibitors. Inactivation was irreversible. The behaviour of both forms of flavocytochrome b2 (lintact and proteolytically cleaved) was examined. It was found that the reduced cleaved enzyme was not inactivated by bromopyruvate; this phenomenon can probably be ascribed to a structural change undergone upon reduction. The value of the lactate dissociation constant of intact cytochrome b2 cytochrome b2 was determined in competition experiments with bromopyruvate. By comparison with the divergent published values for the Ks of the cleaved from, it appears that only those that differ from the Km by a factor of two or three are reasonable. This study opens the way for the identification of an active site residue and localization in the peptide chain of the bifunctional enzyme.

Affinity Labels↗
PubMed1976

Controlled proteolysis of flavocytochrome b2. Characterization of a 15000-dalton heme-binding core and comparison with detergent solubilized cytochrome b5.

It is known that each subunit of the tetrameric flavocytochrome b2 can be cleaved by yeast proteases to fragments of molecular weight 33-36000 and 21 000, with some modification of catalytic properties, but without destruction of the oligomeric state of the protein. We report here experimental conditions which enabled us to simulate this specific cleavage in a controlled fashion with chymotrypsin and subtilisin. With trypsin and papain, on the other hand, it was not found possible to stop the digestion in such a way as to obtain a homogeneous still active product. A characterization of the enzymatic forms obtained by digestion with chymotrypsin and subtilisin at 0 degrees C shows that modification of enzymatic and solubility properties occurs in a stepwise fashion. It is also ccluded that cleavage by yeast proteases is accompanied by loss of 10 to 25 residues. At 37 degrees C, chymotrypsin digestion yields a heme-binding core of molecular weight 15 000, larger than the already characterized tryptic heme-binding core by about 40 residues. Although the latter is known to be very similar to trypsin-solubilized cytochrome b5, the lack of aggregation of the former in aqueous solution, its amino acid composition and circular dichroism spectra do not point to a similarity of its additional peptide segment with the hydrophobic tail of detergent-solubilized cytochrome b5.

Amino Acids↗
PubMed1976

Baker's yeast flavocytochrome b2 (L-(+)-lactate dehydrogenase). An immunological study of structure and function.

Baker's yeast flavocytochrome b2 has been suggested before to be a polyglobular protein formed after a gene fusion process. It is known that one of the potential globules, the heme-binding core, can exist in the absence of the rest of the protein. Using antibodies elicited against the whole enzyme and against the core, we show in this paper that part of the core surface, and in particular the mouth of the heme-binding crevice, must be exposed in the complete enzyme molecule. Antibodies inhibit the activity of intact and proteolytically-cleaved enzymes, which normally show a number of differences in some kinetic parameters. Interestingly, antibodies against the core induce a modification of some kinetic constants for the cleaved enzyme (in particular the Km for the substrate and Ki for D-(-)-lactate, bringing them back to values similar to those for the intact enzyme. These results can be interpreted as a tightening of the cleaved enzyme by anti-core antibodies. The conformational effect is transmitted from the heme-binding region to other parts of the molecule. This implies some intimate contacts between the core and the rest of the protein.

Chemical Phenomena↗
PubMed1976

Complete amino acid sequence of the heme-binding core in bakers' yeast cytochrome b2 (L-(+)-lactate dehydrogenase).

We are reporting here an analysis of the chymotryptic peptides obtained from the tryptic heme-binding fragment of flavocytochrome b2 (cytochrome b2 core). These results completely establish the sequence of the 96 residue-long fragment, for which preliminary evidence has been published before [24]. We also report full experimental details concerning the automatic degradation, the specific cleavages at the unique arginine and methionine residues, and the analysis of the tryptic peptides. In addition, it is shown that the main heme-binding fragment resulting from cytochrome b2 proteolysis by yeast proteases has an additional glutamic acid residue at the C-terminal end relative to the main tryptic heme-binding fragment. The slight sequence modifications presented here (amide groups and insertion of a lysine residue after position 71) do not substantially modify the comparison with liver microsomal cytochrome b5. A new sequence alignment is proposed for the two proteins, and a few structural considerations are presented, based on the inspection of calf liver cytochrome b5 three-dimensional model [50,51].

Amino Acid Sequence↗