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PubMed1991

Distribution of sequences homologous to the impCAB operon of TP110 among bacterial plasmids of different incompatibility groups.

Mutagenic DNA repair is a function of many naturally occurring plasmids belonging to several different incompatibility groups. A DNA probe corresponding to the impCAB operon of the IncI1 plasmid TP110, which encodes such functions, was used to investigate the distribution of homologous sequences in both related and unrelated plasmids. Southern blotting was used to demonstrate considerable sequence conservation amongst a number of plasmid types, with imp-related sequences being found on plasmids belonging to the I1, I1/B, B and FIV incompatibility groups. However, no homology was detected amongst plasmids of the N and L/M incompatibility groups, many of which carry functionally similar gene clusters. It appears that sequences determining mutagenic repair functions have been largely conserved within any one incompatibility group, but that significant divergent evolution has occurred between groups.

Amino Acid Sequence↗
PubMed1982

Sequence homology and recombination between the genomes of morphologically dissimilar bacteriophages LP 52 and theta.

A restriction fragment map of Bacillus licheniformis temperate phage LP 52 DNA (molecular weight 38.5 X 10(6)) was established, using restriction endonucleases BamHI (8 target sites), BglI (10 sites,) BglII (13 sites) and EcoRI (22 sites). The map is linear, with well-defined ends, without any signs of circular permutation. The DNA of a related phage, LP 51, produced identical restriction fragments. At least 62% DNA of LP 52 has been found homologous to the DNA of the recently discovered, morphologically quite dissimilar, phage I, as demonstrated by hybridization of electrophoretically separated restriction fragments of DNA. Under the same conditions, the DNAs of LP 52 and of the morphologically similar Bacillus subtilis phage phi 105 did not cross-hybridize. The homologous regions in the genomes of phages LP 52 and I have been shown to be colinear. Comparison of the cleavage maps of phages LP 52 and I has shown that, within the regions of homology, not a single restriction fragment and few restriction sites have been conserved during divergent evolution. Three major regions of heterology were defined; the longest one, covering the right-hand end of the map (73 +/- 2.75% up to 100% LP 52 genome length) appeared to contain genes coding for structural proteins of the virions; a shorter region at the left-hand end of the map (coordinates zero to 10.3 +/- 3.3% LP 52 genome length) and a very short central region (coordinates 41.8-43.9%) could be identified, the latter apparently containing a regulatory locus responsible for the heteroimmune behavior of the two phages. Recombinants between phages LP 52 and I were isolated. Mapping of recombinant genomes has indicated mutual substitution of allelic pieces of LP 52 and I DNAs upon strict conservation of overall genome length.

Bacteriophages↗
PubMed1984

[New developments concerning the neuron cell membrane: advances in the structural analysis of transmembrane ion channels].

Information processing in the brain requires the activation of electrically and chemically gated ion channels in the neuronal plasma membrane. Recently, the function and the molecular composition of some of these membrane proteins have become the subject of extensive biochemical and biophysical analysis. From the currently available data, it is proposed that the architecture of different neuronal ion channels obeys common structural principles which may have resulted from a divergent evolution of a limited number of ancestor transmembrane polypeptides.

Animals↗
PubMed1982

Drosophila lactate dehydrogenase: molecular and genetic aspects.

(LDH) obtained from larvae of Drosophila melanogaster was purified to homogeneity by affinity chromatography on oxamate-Sepharose. The purification procedure is simple to operate and gives a homogeneous preparation in a good yield (34.86%) after only two steps. Utilizing the homogeneous LDH preparation, an attempt was made to characterize the LDH molecule. Thus, it was found that the N-terminal amino acid is isoleucine, and the enzyme is tetrameric and composed of four identical subunits of apparent molecular weight 38,000, suggesting that it is controlled by a single gene. Homogeneous LDH preparations exhibit one band on neutral acrylamide gels when the substrate is either DL-lactic acid or L-(+)-lactate. The optimum temperature is 45 degrees C for the purified enzyme and 40 degrees C for the crude homogenate. The Km values for pyruvate and NADH are 0.154 and 0.027 mM, respectively, while the Km values for lactate and NAD are 29.4 and 1.33 mM, respectively. A discontinuity in the Ea slope was observed at a transition temperature of 30 degrees C. The Ea value between 20 and 30 degrees C was calculated as 12.06 kcal/mol, while between 30 and 45 degrees C the Ea value was 4.01 kcal/mol. This evidence, together with other observations reported in the literature, suggests that the LDHs of invertebrates and vertebrates have arisen by divergent evolution from a common ancestral gene.

Animals↗
PubMed1984

Alcohol dehydrogenase from Drosophila funebris and Drosophila immigrans: molecular and evolutionary aspects.

Alcohol dehydrogenase from Drosophila funebris and D. immigrans is evident at all developmental stages. The highest activity level appears in third-instar larvae and declines to a lower level at all later stages of development. Both species are monomorphic. The enzyme is a dimer consisting of two identical subunits with molecular weight 27,600. The pI values are 8.6 for D. funebris and 9.02 for D. immigrans. The optimum pH is 8.6 and 8.7 for D. funebris and D. immigrans, respectively. The Km values for NAD+, propan-2-ol, and butan-2-ol are 0.15, 2.90, and 2.08 mM, respectively, for D. funebris and 0.16, 1.53, and 1.49 mM, respectively, for D. immigrans. The half-life for the purified enzyme is 45 days for D. funebris and 18 days for D. immigrans at 4 degrees C. Data on the amino acid composition of both enzymes and peptide maps of alcohol dehydrogenase of D. immigrans reveal that they have marked homologies between them and also with alcohol dehydrogenases of other species. D. funebris shows reduced levels of alcohol dehydrogenase synthesis but has the highest specific activity reported to date for a Drosophila species. D. immigrans synthesises six times more enzyme but the specific activity is comparable to that of other species of Drosophila. This evidence could explain their different alcohol tolerance. The molecular properties of these alcohol dehydrogenases together with other species of Drosophila suggest that the alcohol dehydrogenase of Drosophila has arisen by divergent evolution from a common ancestral gene.

Alcohol Dehydrogenase↗
PubMed1986

Genetic relatedness among animal rotaviruses.

The genomic relatedness among representative rotavirus strains was examined by employing cross-hybridization techniques. Single stranded (ss) RNA prepared by in vitro transcription of purified rotavirus particles and labeled with either 32P or 125I was hybridized to denatured genomic, double stranded (ds) RNAs. The hybrids formed were analyzed by polyacrylamide gel electrophoresis (PAGE) or by testing their sensitivity to digestion with single strand specific nuclease (S-1 nuclease). A relatively high degree of genomic homology was found to exist among several bovine rotavirus strains obtained from different geographical areas. Similarly, a high degree of homology was found between two different simian rotavirus strains, and also between two porcine strains. The human Wa strain exhibited a low degree of genomic homology with simian, bovine and canine strains whereas a higher level of homology was detected between the human Wa strain and the porcine strains. The observed RNA sequence divergences of rotaviruses isolated from different animal species are in agreement with the restricted host range of these viruses and their known antigenic differences and suggest a divergent evolution of their genomes.

Animals↗
PubMed1975

Adaptive character of liver glucokinase.

1. Glucokinase is one of four glucose phosphorylating enzymes present in rat liver. Its distinctive features are a high K-m for glucose (high-K-m isozyme) and a rather narrow substrate specificity. In contrast, the other three enzymes, collectively called hexokinases or low-K-m isozymes, exhibit low K-m values for glucose and a wider substrate specificity. 2. Glucokinase is present in the liver os mammals (with some exceptions), amphibians and lower reptiles; It is absent from higher reptiles and birds. The presence or absence of glucokinase may represent an evolutionary adaptation to feeding habits and other physiological peculiarities. Differences in the immunological behavior and in the kinetic parameters of glucokinases from different taxa suggest the operation of divergent evolution. 3. The levels of glucokinase in rat liver depend strictly on the supply of carbohydrate in the diet. Glycogen phosphorylase and glycogen synthetase behave similarly, whereas other carbohydrate-metabolizing enzymes depend on the provision of either protein or protein plus carbohydrate. Glucokinase decays with a half-life of 33 hr when rats are starved or fed a carbohydrate-free diet, and is induced by the administration of glucose. The adaptive character is not exhibited by all mammals, indicating evolutionary discrimination within the same class and even within the same single order Rodentia. Enzyme adaptation in the liver may partially explain the condition known as 'hunger diabetes'. 4. The endocrine system plays a paramount role in glucokinase adaptation, since insulin is essential for glucose-dependent glucokinase induction and, on the other hand, glucagon, catecholamines and cyclic AMP prevent the induction. Glucocorticoids and some pituitary hormones modulate the rate of induction. The mechanisms underlying the hormonal regulation of glucokinase levels are not well known. 5. The variations in liver glucokinase correspond to changes in the amount of enzyme protein as assessed by immunochemical titration. This fact agrees with the effects of inhibitors of protein synthesis on glucokinase induction. 6. An antiserum against rat glucokinase reacts with the enzyme from mammals and turtles but not with the amphibian enzyme. It does not react with low-K-m hexokinases from different sources. 7. The saturation function for glucose is sigmoidal in mammalian and amphibian glucokinases but not in glucokinase from lower reptiles. The Hill's coefficient is very constant with values about 1.6. The K0.5 (concentration for half saturation) values in the different species studied vary between 1.5 and 8 mM. These kinetic parameters may be considered as another adaptive feature aimed to give maximal efficiency to the liver uptake of glucose at the changeable concentrations in the blood resulting from variations in the amount of dietary glucose.

Adaptation, Physiological↗
PubMed1994

Models of the three-dimensional structures of echidna, horse, and pigeon lysozymes: calcium-binding lysozymes and their relationship with alpha-lactalbumins.

Similarities in amino acid sequences, three-dimensional structures, and the exon-intron patterns of their genes have indicated that c-type lysozymes and alpha-lactalbumins are homologous proteins, i.e., descended by divergent evolution from a common ancestor. Like the alpha-lactalbumins, echidna milk, horse milk, and pigeon eggwhite lysozymes all bind Ca(II). Models of their three-dimensional structures, based on their amino acid sequences and the known crystal structures of domestic hen eggwhite and human lysozymes and baboon and human alpha-lactalbumins, have been built. The several structures have been compared and their relationships discussed.

Amino Acid Sequence↗
PubMedDate not supplied

Divergent regulation of proteoglycan and glycosaminoglycan free chain expression in human keratinocytes and melanocytes.

Keratinocytes and melanocytes, which together form units of structure and function within human epidermis, are known to differ in expression of autocrine growth factors, particularly those with heparin binding affinity. Because such cytokines could be regulated by the endogenous heparinlike glycosaminoglycan, heparan sulfate, proteoglycan synthesis was compared between human keratinocytes and melanocytes cultured from a common donor. Following steady-state isotopic labeling under conditions of active growth (low density cultures) and growth inhibition (high density cultures), the sulfated polymers were isolated from conditioned media and cell extracts. We found that keratinocytes produced substantially more sulfated glycosaminoglycans than did the melanocytes. There was no evidence for hyaluronic acid synthesis by the melanocytes. The majority of [35S]-sulfate labeling was in the heparan sulfates of the keratinocytes and in the chondroitin sulfates of the melanocytes. During the transition from active growth to growth inhibition, there was increased heparan sulfate proteoglycan and free chain synthesis by keratinocytes but not by melanocytes, and chondroitin sulfate proteoglycan production declined in both cell lineages. The differences may reflect divergent evolution as each cell type came to exploit those complex polysaccharides in different ways to regulate molecular pathways of growth and differentiation. The coupling of growth inhibition with augmented synthesis of heparan sulfates observed for the keratinocytes suggests a regulatory role in growth factor signaling in that cell type.

Cell Division↗
PubMed2003

Evolutionary history and mode of the amylase multigene family in Drosophila.

Previous studies indicate that the tandemly repeated members of the amylase (Amy) gene family evolved in a concerted manner in the melanogaster subgroup and in some other species. In this paper, we analyzed all of the 49 active and complete Amy gene sequences in Drosophila, mostly from subgenus Sophophora. Phylogenetic analysis indicated that the two types of diverged Amy genes in the Drosophila montium subgroup and Drosophila ananassae, which are located in distant chromosomal regions from each other, originated independently in different evolutionary lineages of the melanogaster group after the split of the obscura and melanogaster groups. One of the two clusters was lost after duplication in the melanogaster subgroup. Given the time, 24.9 mya, of divergence between the obscura and the melanogaster groups (Russo et al. 1995), the two duplication events were estimated to occur at about 13.96 +/- 1.93 and 12.38 +/- 1.76 mya in the montium subgroup and D. ananassae, respectively. An accelerated rate of amino acid changes was not observed in either lineage after these gene duplications. However, the G+C contents at the third codon positions (GC3) decreased significantly along one of the two Amy clusters both in the montium subgroup and in D. ananassae right after gene duplication. Furthermore, one of the two types of the Amy genes with a lower GC3 content has lost a specific regulatory element within the montium subgroup species and D. ananassae. While the tandemly repeated members evolved in a concerted manner, the two types of diverged Amy genes in Drosophila experienced frequent gene duplication, gene loss, and divergent evolution following the model of a birth-and-death process.

Amylases↗
PubMed2006

Multiple-stress tolerance of ionizing radiation-resistant bacterial isolates obtained from various habitats: correlation between stresses.

Isolation of five ionizing radiation (IR)-resistant bacteria by screening of isolates from various habitats classified as common and stressed is reported. IR-resistant isolates exhibited varying degrees of resistance to gamma-radiation and were classified as highly and moderately radiation resistant. Resistance to ultraviolet (UV) radiation correlated well with gamma-radiation resistance, whereas a comparable desiccation resistance for all the highly and moderately radiation-resistant isolates was observed. However, salt tolerance failed to correlate with IR resistance, indicating a divergent evolution of the salt tolerance and radiation resistance. Characterization of isolates by the amplified rDNA restriction analysis profiling attested to the clustering of these isolates with their stress phenotype. 16S rRNA gene-based analysis of the isolates showed that the bacteria with similar-resistance physiologies clustered together and belonged to related genera. Hydrogen peroxide resistance and mitomycin survival patterns of the isolates indicated the roles of oxidative-stress tolerance in desiccation survival and recombination repair in higher radiation resistance, respectively.

DNA, Bacterial↗
PubMed2002

Molecular characterization of the Pri3 gene encoding a cysteine-rich protein, specifically expressed during fruiting initiation within the Agrocybe aegerita complex.

Coding and regulating sequences of Pri3 (a novel gene specifically expressed in both nucleus types of dikaryons during fruiting initiation) were compared within nine strains of the Agrocybe aegerita complex originating from Europe, Asia and Latin America. Highly homologous coding sequences were found; and the 95-amino-acid-long PRI3 deduced proteins all shared eight cysteines and eight glycines, a putative signal peptide suggesting an extra-cellular localization, a protein kinase C site (T(70)) and a cAMP-dependent kinase site (S(74)). The PRI3 proteins presented no significant homologies with already known proteins and constitute a new class of small cysteine-rich proteins. Within the 5' uncoding regions, two leader introns and a putative upstream regulating sequence resembling the QA1-F activator site were highly conserved. Comparison of the gene sequences within the A. aegerita complex suggested a divergent evolution of the European and Asian/Latin American groups of genes.

5' Flanking Region↗
PubMed2004

Distribution of choline acetyltransferase and NADPH diaphorase in the spinal cord of the pigeon.

Acetylcholine is the neurotransmitter of somatic and autonomic motor systems of the spinal cord. However, there are also intrinsic cholinergic systems which have modulatory functions. Modulatory functions have also been assigned to nitric oxide (NO). Acetylcholine is synthesized by choline acetyltransferase and NO by nitric oxide synthase, which is a NADPH diaphorase. The distribution of both enzymes in the mammalian spinal cord is well known. However, there is a lack of comparative data in avian species. Therefore, the distribution of both enzymes in the spinal cord of the pigeon was studied using histochemical and immunohistochemical methods. Aside from somatic motor neurons and autonomic preganglionic neurons choline acetyltransferase-immunoreactivity was found throughout the spinal cord in lamina III of the superficial dorsal horn and near the central canal. The location of choline acetyltransferase-positive preganglionic neurons in the centrally located column of Terni and the lack of an intermediolateral column typical of the mammalian spinal cord can be confirmed. In lumbosacral segments the axons of centrally located cholinergic neurons crossed to the contralateral side to form a tract in the ventral funiculus, which then innervates the contralateral grey substance. A dense band of NADPH diaphorase staining was found in lamina II and in centrally located neurons of all segments. Part of the centrally located neurons double-labelled for choline acetyltransferase and NADPH diaphorase. In contrast to mammals, preganglionic neurons labelled only weakly for NADPH diaphorase. Altogether, despite the divergent evolution of both classes of vertebrate intrinsic modulatory choline acetyltransferase and NADPH diaphorase systems of birds seem to be largely similar to those of the mammalian spinal cord.

Animals↗
PubMed2005

Expression patterns of STM-like KNOX and Histone H4 genes in shoot development of the dissected-leaved basal eudicot plants Chelidonium majus and Eschscholzia californica (Papaveraceae).

Knotted-like homeobox (KNOX) genes encode important regulators of shoot development in flowering plants. In Arabidopsis, class I KNOX genes are part of a regulatory system that contributes to indeterminacy of shoot development, delimitation of leaf primordia and internode development. In other species, class I KNOX genes have also been recruited in the control of marginal blastozone fractionation during dissected leaf development. Here we report the isolation of class I KNOX genes from two species of the basal eudicot family Papaveraceae, Chelidonium majus and Eschscholzia californica. Sequence comparisons and expression patterns indicate that these genes are orthologs of SHOOTMERISTEMLESS (STM), a class I KNOX gene from Arabidopsis. Both genes are expressed in the center of vegetative and floral shoot apical meristems (SAM), but downregulated at leaf or floral organ initiating sites. While Eschscholzia californica STM (EcSTM) is again upregulated during acropetal pinna formation, in situ hybridization could not detect Chelidonium majus STM (CmSTM) transcripts at any stage of basipetal leaf development, indicating divergent evolution of STM gene function in leaves within Papaveraceae. Immunolocalization of KNOX proteins indicate that other gene family members may control leaf dissection in both species. The contrasting direction of pinna initiation in the two species was also investigated using Histone H4 expression. Leaves at early stages of development did not reveal notable differences in cell division activity of the elongating leaf axis, suggesting that differential meristematic growth may not play a role in determining the observed dissection patterns.

Amino Acid Sequence↗
PubMed1991

Efficiency of transcranial electrostimulation on anxiety and insomnia symptoms during a washout period in depressed patients. A double-blind study.

In order to test the efficacy of cerebral electrostimulation (electrosleep) as an alternative to drug therapy for the treatment of anxiety and insomnia, we conducted a double-blind study in a sample of 21 depressed inpatients submitted to a 5-day period of drug washout on admission to the psychiatric department. During this withdrawal period, anxiety and insomnia were exacerbated in the placebo group, whereas anxiety decreased and sleep duration improved in the active treatment group, with a divergent evolution during the 5-day washout period. The depressive criteria did not respond differentially to treatment, however. Thus, the effects of this drug washout period are markedly attenuated by cerebral electrostimulation, which is of possible interest in the management of psychotropic drug withdrawal.

Adult↗
PubMed1987

Solute carriers involved in energy transfer of mitochondria form a homologous protein family.

The sequences of three mitochondrial carriers involved in energy transfer, the ADP/ATP carrier, phosphate carrier and uncoupling carrier, are analyzed. Similarly to what has been previously reported for the ADP/ATP carrier and the uncoupling protein, now also the phosphate carrier is found to have a tripartite structure comprising three similar repeats of approx. 100 residues each. The three sequences show a fair overall homology with each other. More significant homologies are found by comparing the repeats within and between the carriers in a scheme where the sequences are spliced into repeats, which are arranged for maximum homology by allowing possible insertions or deletions. A striking conservation of critical residues, glycine, proline, of charged and of aromatic residues is found throughout all nine repeats. This is indicative of a similar structural principle in the repeats. Hydropathy profiles of the three proteins and a search for amphipathic alpha-spans reveal six membrane-spanning segments for each carrier, providing further support for the basic structural identity of the repeats. The proposed folding pattern of the carriers in the membrane is exemplified with the phosphate carrier. A possible tertiary arrangement of the repeats and the membrane-spanning helices is shown. The emergence of a mitochondrial carrier family by triplication and by divergent evolution from a common gene of about 100 residues is discussed.

Amino Acid Sequence↗
PubMed1992

Homologous sucrose synthase genes in barley (Hordeum vulgare) are located in chromosomes 7H (syn. 1) and 2H. Evidence for a gene translocation?

The chromosomal location of the two types of sucrose synthase genes, Ss1 and Ss2, has been investigated in barley by Southern blot analysis of wheat-barley addition lines using non-cross-hybridizing-specific probes corresponding to the C-terminal regions of their respective cDNA clones (congruent to 250 bp). The Ss1 gene, whose cDNA of 2,667 bp has been entirely sequenced, is located in the beta-arm of chromosome 7H (syn. 1), while that corresponding to the homologous Ss2 is in the short arm of 2H, suggesting the existence of a translocation event between these two chromosomes in cultivated barley after an initial gene duplication and divergent evolution.

Amino Acid Sequence↗
PubMed1993

The nitrogenase MoFe protein. A secondary structure prediction.

Surface residues, interior residues, and parsing residues, together with a secondary structure derived from these, are predicted for the MoFe nitrogenase protein in advance of a crystal structure of the protein, scheduled shortly to appear in Nature. By publishing this prediction, we test our method for predicting the conformation of proteins from patterns in the divergent evolution of homologous protein sequences in a way that places the method 'at risk'.

Amino Acid Sequence↗