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Biomedical subjects

E Gilson

Publications and source records attributed to E Gilson.

54 records · Page 3Linked to original sources
PubMed1990

Comparative effects of hindlimb suspension and exercise on skeletal muscle myosin isozymes in rats.

The purpose of this study was to ascertain the time course of changes, whilst suspending the hindlimb and physical exercise training, of myosin light chain (LC) isoform expression in rat soleus and vastus lateralis muscles. Two groups of six rats were suspended by their tails for 1 or 2 weeks, two other groups of ten rats each were subjected to exercise training on a treadmill for 9 weeks, one to an endurance training programme (1-h running at 20 m.min-1 5 days.week-1), and the other to a sprint programme (30-s bouts of running at 60 m.min-1 with rest periods of 5 min). At the end of these experimental procedures, soleus and vastus lateralis superficialis muscles were removed for myosin LC isoform determination by two-dimensional gel electrophoresis. Hindlimb suspension for 2 weeks significantly increased the proportion of fast myosin LC and decreased slow myosin LC expression in the soleus muscle. The pattern of myosin LC was unchanged in the vastus lateralis muscle. Sprint training or endurance training for 9 weeks increased the percentage of slow myosin LC in vastus lateralis muscle, whereas soleus muscle myosin LC was not modified. These data indicate that hindlimb suspension influences myosin LC expression in postural muscle, whereas physical training acts essentially on phasic muscle. There were no differences in myosin LC observed under the influence of sprint- or endurance-training programme.

Animals↗
PubMed1988

Evidence for high affinity binding-protein dependent transport systems in gram-positive bacteria and in Mycoplasma.

Gram-negative bacteria are surrounded by two membranes. In these bacteria, a class of high affinity transport systems for concentrating substrates from the medium into the cell, involves a binding protein located between the outer and inner membranes, in the periplasmic region. These 'periplasmic binding-proteins' are thought to bind the substrate in the vicinity of the inner membrane, and to transfer it to a complex of inner membrane proteins for concentration into the cytoplasm. We report evidence leading us to propose that a Gram-positive bacterium, Streptococcus pneumoniae, and a mycoplasma, Mycoplasma hyorhinis, which are surrounded by a single membrane and have therefore no periplasmic region, possess an equivalent to the high affinity periplasmic binding-protein dependent transport systems, i.e. extra-cytoplasmic binding lipoprotein dependent transport systems. The 'binding lipoproteins' would be maintained at proximity of the inner membrane by insertion of their N-terminal glyceride-cysteine into this membrane.

Amino Acid Sequence↗
PubMed1987

Species specificity of bacterial palindromic units.

We described previously a family of dispersed palindromic sequences highly repeated in Escherichia coli and Salmonella typhimurium genomes. These sequences, called PU (palindromic units), are located outside structural genes. We report here observations suggesting that PU may have a role in bacterial speciation.

Base Sequence↗
PubMed1986

Palindromic units from E. coli as binding sites for a chromoid-associated protein.

Several hundred copies of a highly conserved extragenic palindromic sequence, 20-40 nucleotides long, exist along the chromosome of E. coli and S. typhimurium. These have been defined as palindromic units (PU) or repetitive extragenic palindromes (REP). No general function for PUs has been identified. In the present work, we provide data showing that a protein associated with a chromoid extract of E. coli protects PU DNA against exonuclease III digestion. This provides the first experimental evidence that PU constitutes binding sites for a chromoid-associated protein. This result supports the hypothesis that PUs could play a role in the structure of the bacterial chromoid.

Bacterial Proteins↗
PubMed1986

malM, a new gene of the maltose regulon in Escherichia coli K12. I. malM is the last gene of the malK-lamB operon and encodes a periplasmic protein.

The structure and expression of the distal part of the malK-lamB operon in Escherichia coli was studied. DNA sequencing was performed as far as a HinfI restriction site located 1313 base-pairs downstream from gene lamB. The open reading frame, formerly called molA, which begins 245 base-pairs downstream from gene lamB, is longer than was initially thought, and was renamed malM. It could encode a protein of 306 amino acid residues. The complete malM open reading frame was cloned under control of the tac 12 promoter. In maxicells, the resulting plasmid permitted tac12-promoted synthesis of two polypeptides, encoded by gene malM, with apparent molecular weights of 37 X 10(3) and 34.5 X 10(3). We provide strong evidence that the 34.5 X 10(3) Mr protein is derived from the 37 X 10(3) Mr protein by processing at the amino-terminal end, and that this processed form is located in the periplasmic space. We show that the chromosomal malM gene is expressed as part of the malK-lamB operon, and that its product is periplasmic. Finally, we demonstrate with nuclease S1 mapping experiments that the mRNA terminates at a typical rho-independent terminator located about 45 base-pairs beyond the end of gene malM, which is thus the last gene of the malK-lamB operon.

Amino Acid Sequence↗
PubMed1986

malM, a new gene of the maltose regulon in Escherichia coli K12. II. Mutations affecting the signal peptide of the MalM protein.

malM is the last gene of the malK-lamB-malM operon of Escherichia coli K12. It encodes a periplasmic protein. Mutations affecting the hydrophobic core of the N-terminal extension of the MalM protein have been isolated. They result in an increase in amount and specific activity of a MalM-LacZ hybrid protein. This result confirms that the signal peptide of the MalM protein is functional.

Base Sequence↗
PubMed1984

A family of dispersed repetitive extragenic palindromic DNA sequences in E. coli.

We report the properties of 67 members of a family of dispersed repetitive palindromic extragenic bacterial DNA sequences. These sequences, called palindromic units, appear to be present at least several hundred times outside structural genes on the Escherichia coli chromosome. They are found either in clusters - as in a previously described intercistronic element - or in single occurrences. They are not only found within an operon but also between different operons, including between convergent ones. The palindromic units could yield a stem and loop structure at the level of DNA or RNA. The base of the stem is made of eight remarkably conserved base pairs while the rest varies somewhat in length and sequence. We analyse the data available on the palindromic units and we speculate on their possible roles with emphasis on transcription and mRNA stability or processing, as well as on their possible relation to transposition elements and the modular evolution of the genome.

Base Sequence↗
PubMed1982

Sequence of the malK gene in E.coli K12.

We present the sequence of gene malK which encodes a component of the system for maltose transport in E.coli K12. We also determined the position of deletion (S50) which fuses malK to the following gene lamB; the malK-lamB protein hybrid contains all of the malK protein. The mRNA corresponding to the last two thirds of gene malK could form stable stem and loop structures. The malK protein, as deduced from the gene sequence, would include 370 residues and correspond to a molecular weight of 40700. The sequence as well as sequence comparisons with the ndh protein of E.coli are discussed in terms of the location and function of the malK protein.

ATP-Binding Cassette Transporters↗
PubMed1982

Extensive homology between membrane-associated components of histidine and maltose transport systems of Salmonella typhimurium and Escherichia coli.

A strong homology was found between the amino acid sequences, deduced from DNA nucleotide sequences, of cytoplasmic membrane-associated components of the high affinity histidine transport system of Salmonella typhimurium (coded by the hisP gene) and the maltose-maltodextrin transport system of Escherichia coli (coded by the malK gene). When the HisP protein sequence was aligned with that of the NH2-terminal two-thirds of the MalK protein, 32% of the positions were identical, and an additional 35% were occupied by functionally similar amino acid residues. These results suggest that some, and possibly many, "periplasmic-binding protein-dependent" transport systems have evolved from a common ancestral system.

ATP-Binding Cassette Transporters↗
PubMedDate not supplied

Imaging the asymmetrical DNA bend induced by repressor activator protein 1 with scanning tunneling microscopy.

The yeast Repressor Activator Protein 1 (RAP1) binds a 13-bp consensus found in many transcriptional regulatory regions, in silencer elements, and in telomeric repeat DNA of Saccharomyces cerevisiae. Gel retardation assays suggest that RAP1 bends DNA as it binds, with the vertex of the angle located 5' of the consensus. We show that removal of 230 aa in the N-terminus of RAP1 reduces the aberrant electrophoretic mobility of the protein-DNA complex, while removal of a C-terminal domain of RAP1 causes even greater distortion. To demonstrate that the aberrant electrophoretic mobility is really due to a bend in the double helix, the RAP1-DNA complex was analyzed by Scanning Tunnelling Microscopy (STM). The efficiency and accuracy of binding is checked in parallel by standard Transmission Electron Microscopy (TEM). Due to the use of high-angle shadowing of freeze-dried samples at low temperatures, the STM images allow us to confirm that RAP1 binding induces a DNA bend > 50 degrees, while the binding of the minimal DNA-binding domain shows significantly less distortion of the DNA helix.

DNA↗
PubMedDate not supplied

Palindromic unit highly repetitive DNA sequences exhibit species specificity within Enterobacteriaceae.

Palindromic units (PU, or REP for repetitive extragenic palindrome) constitute a family of DNA sequences of 40 nucleotides which is highly repeated in the genome of Escherichia coli. We analysed the presence of PU sequences in 99 different bacterial genomes by cross-hybridization. When PU sequences were used as a probe, only DNA from Enterobacteriaceae closely related to E. coli exhibited an appreciable hybridization signal: Shigella sonnei, Shigella boydii, Salmonella enteritica serotype Typhimurium, Citrobacter freundii and Levinea malonatica. Furthermore, these bacteria could be divided into two groups which corresponded to a slight difference in their PU sequence: the E. coli group includes S. sonnei and S. boydii; the S. enteritica serotype Typhimurium group includes C. freundii and L. malonatica.

Blotting, Southern↗
PubMedDate not supplied

The BIME family of bacterial highly repetitive sequences.

Palindromic units (PU or REP) were initially defined as a DNA sequence of 40 nucleotides which is highly repeated in the genome of several enterobacteria and found in clusters of up to six copies. It appears now that PU belong to a larger repeated DNA element, of up to 300 nucleotides, called BIME for bacterial interspersed mosaic element. BIME is a mosaic combination of ten small DNA motifs, including the PU sequence. A central question concerning BIME is to determine whether they play a critical role within the cell. BIME exhibit only limited effects on local gene expression; it seems unlikely that these weak effects alone can account for the high BIME sequence homogeneity. It has recently been shown that DNA gyrase and DNA polymerase I are able to specifically recognize BIME DNA in vitro. These findings suggest that BIME could play a role in the functional organization of the bacterial nucleoid. Hypotheses on their origin and evolution are discussed.

Base Sequence↗
PubMedDate not supplied

A subfamily of E. coli palindromic units implicated in transcription termination?

We previously described a family of dispersed palindromic sequences highly repeated in Escherichia coli and Salmonella typhimurium genomes. These sequences, called PU (palindromic units), are located outside structural genes. Conflicting results have been reported on the effects of different PU in transcription termination. Two PU located between co-transcribed genes in S. typhimurium were found not to cause transcription termination [25]. One PU located between convergently transcribed genes in E. coli behaved as bidirectional transcription terminators [12]. In the present paper, we show that three PU located between co-transcribed genes in E. coli are not a transcription terminator. From the literature, we define a subfamily of PU, which we called PU, located between convergently transcribed genes which we implicate in bidirectional transcription termination. This plus the analysis of another PU which terminates transcription suggest that pecularities in the sequence or in the sequence environment of PU determine their role in transcription termination.

Escherichia coli↗
PubMedDate not supplied

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France↗