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H Zuber

Publications and source records attributed to H Zuber.

At least 91 records · Page 5Linked to original sources
PubMed1981

The complete amino acid sequence of both subunits of allophycocyanin, a light harvesting protein-pigment complex from the cyanobacterium Mastigocladus laminosus.

The amino acid sequences of the alpha- and beta-subunit of allophycocyanin, a water-soluble light-harvesting protein-pigment complex from the thermophilic cyanobacterium Mastigocladus laminosus have been determined. The alpha-chain consists of 160 amino acid residues and the beta-chain of 161 amino acid residues. The homology of the alpha- and beta-chains is 37%. A comparison with C-phycocyanin reveals that the second chromophore of the C-phycocyanin beta-subunit is attached to an inserted peptide of 10 amino acid residues at position 151-160.

Amino Acid Sequence↗
PubMed1980

Amino acid sequence analysis of fragments generated by partial proteolysis from large simian virus 40 tumor antigen.

Large simian virus 40 tumor antigen was bound as immune complex to protein A-Sepharose and then subjected to limited proteolysis which yielded several discrete fragments. Primary structures near the cleavage sites were determined by radiosequencing techniques. Experimental data for five fragments matched an amino acid sequence predicted from a nucleotide sequence at 0.51 map unit of the viral genome. We have thus identified the reading frame of translation beyond the intervening sequence at 0.60 to 0.53 map units. A cleavage map of tumor antigen was established on the basis of the sequence data and of the apparent molecular weights of the fragments. The bond most susceptible to cleavage by trypsin was between arginine-130 and lysine-131 in a cluster of five basis amino acids. Other cleavage sites were located in the COOH-terminal half of tumor antigen. Each fragment was analyzed by complete tryptic proteolysis and peptide mapping on an ion exchange column. Peaks occurring in the peptide map of large tumor antigen could thus be assigned to different segments of the protein. Two specific regions of tumor antigen were shown to be phosphorylated.

Amino Acid Sequence↗
PubMed1980

Isolation and characterization of the polypeptide components from light-harvesting pigment-protein complex B800--850 of Rhodopseudomonas capsulata.

The light-harvesting bacteriochlorophyll-carotenoid-protein complex B800--850 has been isolated from membranes of the phototroph-negative mutant strain Y5 of Rhodopseudomonas capsulata. The three polypeptides of the complex have been found to be soluble in chloroform-methanol (1:1, v/v) in the presence of 0.1 M ammonium acetate. They were extracted from the complex and separated by gel filtration on Sephadex LH-60 in the same solvent mixture. Minimum molecular weights based on amino acid composition are 12 000, 9300, and 5100. Values previously determined by sodium dodecyl sulfate/polyacrylamide gel electrophoresis are 14 000, 10 000 and 8000. The two smaller polypeptides (polarities 31% and 39%) are completely soluble in chloroform/methanol/ammonium acetate while the largest and most polar (41%) polypeptide is only partially soluble. The largest polypeptide contains no tryptophan. The middle polypeptide contains no cysteine and arginine, while the small polypeptide lacks cysteine. Methionine is shown to be the amino terminus for the small and middle polypeptides by two independent methods (Edman degradation and dansylation). Both methods also indicated that the N terminus of the 14 000 polypeptide seems to be blocked. Partial N-terminal amino acid sequences were obtained for the two smaller polypeptides. No homology between the two proteins was observed.

Amino Acids↗
PubMed1979

Thermal stability and protein structure.

Amino acid sequences have been compared for thermophilic and mesophilic molecules of ferredoxin, glyceraldehyde-3-phosphate dehydrogenase, and lactate dehydrogenase. It is shown that Gly, Ser, Ser, Lys, and Asp in mesophiles are generally substituted by Ala, Ala, Thr, Arg, and Glu, respectively, in thermophiles. These exchanges suggest that thermal stability can be achieved by the addition of many small changes throughout the molecule without significant change in the backbone conformation. Their overall effect is primarily to increase internal and decrease external hydrophobicity as well as to favor helix stabilizing residues in helices. These substitutions minimize interruption of function or internal residue packing arrangements. Although the analysis has been confined to the above-mentioned molecules, the observed stabilizing principles may be more generally applicable.

Amino Acid Sequence↗
PubMed1979

Properties of allophycocyanin II and its alpha- and beta-subunits from the thermophilic blue--green alga Mastigocladus laminosus.

Purified allophycocyanin II and its subunits have been examined with respect to spectroscopic properties, sedimentation, reconstitution and isoelectric behaviour. In 0.02m-potassium phosphate buffer, pH8.0, and at a concentration of 0.25mg/ml, allophycocyanin II and its alpha- and beta-subunits show visible absorption maxima at 650, 615 and 615nm respectively, whereas the fluorescence emission maxima were determined to be at 662, 640 and 630nm respectively. The absorption difference spectrum (dilution difference) of allophycocyanin II displays maxima at 650 and 590nm with a minimum at 610nm. The c.d. spectrum of allophycocyanin II showed only one positive-ellipticity band at 635nm, and a major negative-ellipticity band at 340nm. Oxidation of allophycocyanin II, low- and high-pH solutions (pH3.0 and 11.0), various ethanol concentrations as well as dialysis against distilled water induce a spectral change leading to phycocyanin-like characteristics. In most cases these shifts are reversible. Allophycocyanin II is thermostable over a period of 60min at temperatures up to 60 degrees C. The isoelectric points of allophycocyanin II and its alpha- and beta-subunits are 4.65, 4.64 and 4.82 respectively. Estimated molecular weights from sedimentation-equilibrium analyses were 102500 for allophycocycanin II, 16000 for the alpha- and 31500 for the beta-subunit. Recombination of alpha- and beta-subunits leads to allophycocyanin II, which is indistinguishable from native allophycocyanin with respect to its spectral form, to its gel-filtration and to its electrophoretic behaviour.

Cyanobacteria↗
PubMed1979

Hydrophobic membrane protein from chromatophores of Rhodospirillum rubrum. Structural and spectroscopic studies of monolayers and multilayers.

A hydrophobic, lipid- and pigment-free polypeptide from the chromatophore membrane of Rhodospirillum rubrum was spread from chloroform/methanol, pyridine and formic acid solutions at an air-water interface. Surface pressure versus area isotherms of the monolayers formed at the interface were partially dependent upon the spreading solvent used. From the surface area at 20 dynes/cm compression, an average molecular area of 12.9 nm2/molecule was calculated for a polypeptide monolayer spread from chloroform/methanol. Multilayers built up on germanium plates at different surface pressures were subjected to attenuated total reflection infrared spectroscopy. In all cases the amide I and II absorption bands were typical of alpha-helical and random conformations. Electron microscopy of transferred monolayers replicated by rotary platinum shadowing revealed domains of regular texture in specimens prepared at 20 dynes/cm. Such domains were virtually absent in specimens prepared at 10 and 30 dynes/cm. Light optical diffractometry of the ordered arrays yielded a smallest repetitive area of 13.5 nm2 which agrees well with the molecular area obtained from the monolayer surface. Although no drastic changes in secondary structure were detected in the course of this study, some conformational changes are indicated by solvent-dependent differences in the surface pressure versus area isotherms.

Bacterial Chromatophores↗
PubMed1979

Structure and function of L-lactate dehydrogenases from thermophilic and mesophilic bacteria. I) Isolation and characterization of lactate dehydrogenases from thermophilic and mesophilic bacilli.

Lactate dehydrogenases from thermophilic bacilli (Bacillus stearothermophilus, Bacillus caldotenax) and from mesophilic bacilli (Bacillus X1, Bacillus subtilis) have been isolated by a two-step purification procedure. Only one type (LDH-P4) composed of four identical subunits (Mr 34 000 or 36 000) was found in each bacillus. The tetrameric enzymes were characterized with respect to thermostability, pH and temperature dependence of the pyruvate reduction and the L-lactate oxidation, substrate specificity, saturation kinetics (Km values of pyruvate, lactate, NAD, NADH), pyruvate and oxamate inhibition, and activation by fructose bisphosphate. The thermophilic and mesophilic enzymes differ characteristically in these parameters. Preliminary structural data (amino acid composition, comparative N-terminal sequence analysis) show the expected close phylogenetic relationship (high degree of sequence homology), but also typical differences between thermophilic and mesophilic dehydrogenases, a suitable basis for further comparative studies.

Bacillus↗
PubMed1978

The complete amino acid sequence of both subunits of C-phycocyanin from the cyanobacterium Mastigocladus laminosus.

The amino acid sequences of both subunits of the C-phycocyanin from the thermophilic cyanobacterium Mastigocladus laminosus have been determined. The alpha-chain consists of 162 amino acid residues and has a molecular weight of 18000, whereas the beta-chain consists of 172 residues and has a molecular weight of 19400. For the first three quarters of their length the polypeptide chains are 31% homologous, whereas there is no significant homology in the final quarter up to the C-terminus. This could mean that the introduction of an additional chromophore binding site in the last quarter of the beta-chain during evolution was achieved via a large number of point mutations or by exchange of the whole C-terminal part in an ancestral gene.

Amino Acid Sequence↗
PubMed1977

Thermophilic aminopeptidase. IV. Cooperative effects in ANS binding by the thermophilic aminopeptidase I from B. stearothermophilus.

Aminopeptidase I is a membrane-bound metalloenzyme isolated from B. stearothermophilus which is thermostable and requires Co2+ for activity. The Co, Zn, and metal-free enzyme were titrated with ANS, and cooperative binding was noted with the active Co enzyme but not with the Zn (5% active) or apo (inactive) enzymes. There are a number of sites for ANS on each of the three enzyme forms and the agreement between the association constants of the Zn enzyme (identical and independent sites) and the non-cooperative sites of the Co enzyme suggest that these sites are intrinsically similar. However, binding to the first of these sites in the Co enzyme triggers a cooperative binding of a second molecule of ANS, and this cooperative binding is related to a concomitant decrease in enzymatic activity. The correspondence can be shown by comparison of the inhibition constant for the hydrolysis of Gly-Leu-Tyr (Ki-1=13,300 cm3/mmol) and the association constant for the cooperating site (12,500 cm3/mmol). The significance of these observations is discussed in terms of the nature of the binding sites and the possible consequences of the interactions on the regulation of aminopeptidase I activity.

Aminopeptidases↗
PubMed1976

Aminopeptidase II from Bacillus stearothermophilus.

1. The low molecular weight aminopeptidase (aminopeptidase II) from Bacillus stearothermophilus cells grown at 50 degrees C was purified to a homogeneous state. 2. Molecular weight determination by sodium dodecyl sulfate gel electrophoresis resulted in a value of 46 000 for the subunits. A molecular weight of 80 000-100 000 has been reported for the native enzyme. We therefore conclude that aminopeptidase II is a dimeric enzyme. 3. The amino-terminal sequence, the amino acid analysis and the subunit molecular weight of aminopeptidase II show no relationship to the corresponding data of aminopeptidase I. 4. Aminopeptidase II binds two Co2+ per subunit. The dissociation constants of these ions determined by binding studies and by kinetic analysis agree within experimental error.

Amino Acids↗
PubMed1976

Thermophilic and mesophilic enzymes from B. caldotenax and B. stearothermophilus: properties, relationships and formation.

1) The adaptive system of thermophilic bacteria, as demonstrated with B. caldotenax, seems to be suitable to produce thermophilic and mesophilic enzymes for comparative studies. 2) If it may be assumed that the extensive homologies in the N-terminal sequences of the LDHs also extend over the entire polypeptide chain, comparison of these sequences together with investigation on the 3-dimensional structure offer the possibility of elucidating those structural details which may be responsible for thermostability and the other thermophilic properties. However, the difficulty still remains that the latter may be obscured by differences not related to thermostability etc. Neverthless it may be hoped that comparison of the full sequences of not only the LDHs but also of a sufficient number of other enzymes of the same system will yield such details. 3) A further interesting goal with respect to the mechanism of enzyme adaptation would be reached if the differences in amino acid sequence of thermophilic and mesophilic LDH enzymes would throw light on the type of the amino acids always being exchanged. Here from the very hypothetical point of view the question arises as to whether the bacterial cell during the metabolic adaptation process or even by mutation/selection is able to modify just those few amino acid residues thermodynamically important for thermostability. Alternatively: does there exist a "rule" by which certain amino acid residues are invariably exchanged on a change for thermophilic to mesophilic enzymes? 4) Problems not mentioned here arise with B. stearothermophilus, which can be adapted poorly via the spores or on intermediate temperatures. Of great importance, but also a special problem in these studies on thermophilic and mesophilic enzymes produced by the same bacterium are a) the characterization of the thermophilic (70 degrees or 55 degrees) and mesophilic (37 degrees) bacterial variants (in respect to type), b) the control of homogeneity of the bacterial culture (contamination, mixed population), c) proof of the genetic identity of the 70 degrees- (55 degrees-) and 37 degrees -variant of B. caldotenax and B. stearothermophilus, which differ greatly in their phenotypes, for example in their metabolism, cell- or colony merphology. The taxonomical-biochemical identity or also the identity of morphology of the sporangia, since this should be an expression of the temperature dependent phenotype, cannot be used unconditionally as criteria of identity. Criteria such as the presence of identical enzymes in both variants or the identity of the genome (use of genetic markers, anlaysis of the DNA) are more reliable. Experiments with both variants of B. caldotenax demonstrated an identically high content of cytosine plus guanine in their DNA: 62.2% in the thermophilic DNA and 66.8% in the mesophilic DNA. In the thermophilic B. stearothermophilus the C+G content of the DNA was 56.5% and in the mesophilic variant 57.1%...

Adaptation, Physiological↗