Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

E. coli K12 was found to utilise both D-and L-stereoisomers of alanine as sole sources of carbon, nitrogen and energy for growth. This capability was absolutely dependent upon the possession of an active membrane-bound D-alanine dehydrogenase, and was lost by mutants in which the enzyme was defective. The Michaelis constant for the enzyme with D-alanine as substrate was 30 mM, and the pH optimum about 8.9. D-alanine was the most active substrate, L-alanine was inactive and several other D-amino acids were 10--50% as active as D-alanine. Oxidation of D-alanine was linked to oxygen via a cytochrome-containing respiratory chain. Synthesis of the dehydrogenase was induced 16 to 23-fold by incubation with D- or L-alanine, but only D-alanine was intrinsically active as an inducer. L-alanine was active either as a substrate or inducer only in t he presence of an uninhibited alanine racemase which converted it to the D-isomer. The map-location of their structural genes between ara and leu, together with other similarities, indicate that D-alanine dehydrogenase and the "alaninase" of Wijsman (1972a) are the same enzyme. Both D- and L-alanine were intrinsically active as inducers of alanine racemase synthesis. The synthesis of both D-alanine dehydrogenase and alanine racemase was found to be regulated by catabolite repression.
Mol Gen Genet 1976 Dec 08
PMID:Biochemical, genetic, and regulatory studies of alanine catabolism in Escherichia coli K12. 1 92

The pH-dependence of the reduction rate of ferricytochrome C by intact and chemically modified oxymyoglobins has been studied. The modification was performed with respect to histidine residues and alpha-aminogroup of N-terminal valine. Two histidine residues of myoglobin, His A10 and His GH1, are shown to take part in the realization of the "active" contact between the molecules in the course of the reaction. The deprotonation of the first residue contributes to the acceleration and that of the second to the reduction of the reaction. The found orientation of the Mb molecules in the "active complex" implies that at any orientation of cytochrome C the distance between the haemes of the both molecules should be more than 30 A. This makes highly probable that a structure-dependent mechanism of electron transfer in the system under study can be proposed.
Mol Biol (Mosk)
PMID:[Electron transfer to hemoproteins. II. pH-dependence of the reduction rate of ferricytochrome c by oxymyoglobin]. 3 34

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.
 ...
PMID:Surface differences and similarities in two homologous proteins. Cytochrome b5 and cytochrome b2 core. 10 Dec 51

A nuclear gene mutant of Neurospora crassa designated cyb-3 is deficient in cytochrome b and coenzyme QH2-cytochrome c reductase. Nearly normal when grown at 25 degrees C, the strain expresses a mutant phenotype at 38 degrees C. Mitochondria from cyb-3 mycelium, which has undergone 3-4 mass doublings at the elevated temperature, possess 3-fold less cytochrome b, 2-fold more cytochrome, c, 5-fold less coenzyme QH2-cytochrome c reductase activity, and require 3-fold less antimycin A per milligram of protein to inhibit NADH oxidation that do wild type mitochondria. The activity of coenzyme QH2-cytochrome c reductase declines rather slowly in cultures of cyb-3 transferred to 38 degrees C, and the in vitro thermostability of the enzyme is very similar in wild type and mutant mitochondria. Therefore, the mutation may decrease synthesis of impair integration into the membrane of cytochrome b and perhaps other proteins of the enzyme comple.
Mol Gen Genet 1977 Mar 28
PMID:A temperature-sensitive mutant of Neurospora crassa deficient in cytochrome b. 14 Oct 3

The extranuclear mitochondrial oligomycin-resistant mutation of Aspergillus nidulans, (oliA1), was transferred asexually into four nuclear oligomycin-resistant strains of different phenotypes. In all four cases, the possession of the nuclear plus extranuclear mutation led to an increase in the in vivo level of oligomycin resistance. In two cases, the altered cytochrome spectrum and impaired growth ability determined by (oliA1) were suppressed by the nuclear mutations. In the third case, the in vitro oligomycin resistance of the double mutant ATPase was dramatically increased above that of either of the component single mutant strains, indicating a synergystic interaction between the nuclear and extranuclear gene products. In the fourth case, the double mutant became cold-sensitive. A new extranuclear mitochondrial oligomycin-resistant mutation (oliB332) is described. This mutant is phenotypically similar to, though not identical with, (oliA1) but is separable by recombination. A range of nuclear oligomycin-resistant mutants have been mapped. Despite presenting five distinctly different phenotypes, they all map at the same locus.
Mol Gen Genet 1977 Sep 09
PMID:Nuclear-extranuclear interactions affecting oligomycin resistance in Aspergillus nidulans. 14 64

We have previously isolated six non-allelic, nuclear mutations (sui loci) that partially suppress the growth, respiratory and cytochrome abnormalities of the extranuclear [poky] mutant. A comparison of the mitochondrial ribosome profiles of suppressed and unsuppressed [poky] strains revealed that five of the six suppressors alleviate at least partially the deficiency of mitochondrial small ribosomal subunits that is associated with the [poky] genotype. Six independently isolated Group 1 extranuclear mutants, namely [exn-1], [exn-2], [exn-4-a1, [stp-b1], [SG-1] and [SG-3-A1, which have growth and cytochrome phenotypes similar to [poky] also were found to be deficient in small subunits of mitochondrial ribosomes. Using cytochrome aa3 and b production as a criterion for mitochondrial protein synthesis, it could be shown that the nuclear su I suppressors of [poky] also suppress the other six Group I extranuclear mutants. However, differences in the efficiencies of suppression by suI suppressors suggest that at least some of Group I extrachromosomal mutants are not simply re-isolates of [poky], but represent distinct extranuclear mutations.
Mol Gen Genet 1978 May 31
PMID:Nuclear suppressors of the [poky] cytoplasmic mutant in Neurospora crassa. III. Effects on other cytoplasmic mutants and on mitochondrial ribosome assembly in [poky]. 14 10

1. Oxidative phosphorylation and respiratory enzyme activities were measured in the mitochondria from the non-involved lobe of the liver in eighteen patients with massive tumour mainly localized to one lobe and from the regenerating livers of partially hepatectomized rats treated with chloramphenicol. 2. In patients, the concentrations of cytochrome a(t) varied from 40 to 170 pmol/mg of protein. In mitochondria with cytochrome a(t) concentrations more than 70 pmol/mg of protein, the phosphorylative activity per mg of mitochondrial protein was considerably higher than in controls. The mitochondrial oxidative and phosphorylative activities per unit of cytochrome a(t) were negatively correlated with the concentration of cytochrome a(t). These patients with mitochondrial cytochrome a(t) exceeding 70 pmol/mg of protein tolerated partial hepatectomy well. On the other hand, in patients with mitochondrial cytochrome a(t) less than 60 pmol/mg of protein, phosphorylative activity was very low and there was a high surgical mortality. 3. In the regenerating liver of rats treated with chloramphenicol, the oxidative and phosphorylative activities per unit of cytochrome a(t) were negatively correlated with the concentration of cytochrome a(t). 4. It is suggested that an increase in ATP-synthesizing activity per unit of respiratory assemblies is the most basic homeostatic mechanism maintaining energy production in response to an increased metabolic load upon hepatic cells.
Clin Sci Mol Med 1975 Feb
PMID:Control of phosphorylative activity in human liver mitochondria through changes in respiratory enzyme contents. 16 18

A statistical analysis aimed at obtaining some informations on a possible correlation between simultaneous amino acid substitutions is proposed. This method is applied to a set of cytochrome C, at the level of tandem and triple substitutions separated along the peptide chain by 1 to 15 peptide bonds. Monte-Carlo simulations are performed and the results are compared. We find a significant occurrence of three adjacent amino acid substitutions in which the first replacement requires a two nucleotide substitution. A possible explanation of this fact is proposed on the basis of covarions.
J Mol Evol 1975 Aug 05
PMID:Study of double and triple simultaneous substitutions of amino acids in cytochromes C. 16 58

Using many more cytochrome sequences than previously available, we have confirmed: 1, the eukaryotic cytochrome c diverged from a common ancestor; 2, the ancestral eukaryotic cytochrome c was not greatly different in character from those present today; 3, fixations are non-randomly distributed among the codons, there being evidence for at least four classes of variability; 4, there are similar classes of variability when the data are considered according to the nucleotide position within the codon; 5, the number of covarions (concomitantly variable codons) in mammalian cytochrome c genes is about 12 and the same value has been obtained for dicotyledenous plants as well; 6, all of the hyper- and most highly variable codons are for external residues, nearly 60 per cent of the invariable codons are for internal residues and nearly half of the codons for internal residues are invariable; 7, the first nucleotide position of a codon is more likely and the second position less likely to fix mutations than would be expected on the basis of the number of ways that alternative amino acids can be reached; 8, the character of nucleotide replacements is enormously non-random, with G-A interchanges representing 42% of those observed in the first nucleotide position, but the observation does not stem from a bias in the DNA strand receiving the mutation, nor from the presence of a compositional equilibrium, nor from a bias in the frequency with which different nucleotides mutate, but rather from a bias in the acceptability of an alternative nucleotide as circumscribed by the functional acceptability of the new amino acid encoded; and 9, the unit evolutionary period is approximately 150 million years/observable (amino acid changing) nucleotide replacement/cytochrome c covarion in two diverging lines. Wherever non-randomness has been observed, it has always been consistent with the consideration that an alternative amino acid at any location is more likely to be acceptable the more closely it resembles the present amino acid in its physico-chemical properties. Finally, in no case did the a priori assumption of a biologically realistic phylogeny lead to any observations or conclusions that were in any way significantly different from those obtained when the phylogeny was based solely upon the sequences, proving that the earlier results were not a consequence of some internal circularity.
J Mol Evol 1976 Jun 23
PMID:The molecular evolution of cytochrome c in eukaryotes. 18 84

A noncovalent complex of the apoprotein (1-104) and cyanogen bromide heme fragment containing residues 1 to 65, (1-65) H, has been prepared from horse heart cytochrome c. Conditions under which the redundant portions of the ferrous complex can be removed by limited trypsin digestion have been devised. The complementing fragments have been isolated from the derived complexes and four apofragments and one heme fragment have been identified in the amino acid sequence of cytochrome c. They are (39-104), (40-104), (54-104), (56-104), and (1-53)H. The formation of an ordered ferric complex composed of one heme fragment and one apofragment for the cases (1-53)H (39-104), (1-53)H-(40-104), (1-53)H-(54-104), and (1-53)H-(56-104) has been demonstrated by the quenching of the tryptophan 59 fluorescence and the regain of biological activity in a cytochrome b2 assay. The apparent dissociation constant has been estimated as less than 3 X 10(-7) M in all the aforementioned cases. Thus, the region (between residues 38 and 57) of the amino acid sequence permissible for cleavage without disruption of the ordered structure indicated by the present in vitro experiments corresponds to that (between residues 38 and 57) evolutionally deleted in the three-dimensional structure of Pseudomonas aeruginosa cytochrome c551 discovered by Dickerson et al. (Dickerson, R.E., Timkovich, R., and Almassy, R.J. (1976) J. Mol. Biol. 100, 473-491).
 ...
PMID:Formation of a biologically active, ordered complex from two overlapping fragments of cytochrome c. 19 Feb 31


1 2 3 4 5 6 7 8 9 10 Next >>