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L M Hall

Publications and source records attributed to L M Hall.

At least 109 records · Page 6Linked to original sources
PubMed1989

Cloning, sequence analysis and chromosome localization of a Drosophila muscarinic acetylcholine receptor.

Two cDNA clones (3.7 kb and 4.8 kb) encoding a Drosophila muscarinic acetylcholine receptor were isolated from a Drosophila head cDNA library and characterized by automated DNA sequence analysis. The Drosophila muscarinic receptor contains 788 amino acids with a calculated Mr of 84,807 and displays greater than 60% homology with mammalian muscarinic receptors. The muscarinic receptor maps to the tip of the right arm of the second chromosome of the Drosophila genome.

Amino Acid Sequence↗
PubMed1989

Methicillin-resistant Staphylococcus aureus from China characterized by digestion of total DNA with restriction enzymes.

A series of clinical isolates of methicillin resistant Staphylococcus aureus (MRSA) from two hospitals in China was examined. Fragment patterns obtained by digestion of total cellular DNA with restriction enzymes were used to characterize the isolates, in combination with phage-typing, antibiotic resistance profile, and plasmid profile. Digestion of total cellular DNA with restriction enzymes was most useful in discriminating between isolates and yielded additional information on the relatedness of non-identical isolates. In one hospital a single strain, resistant to a large number of antibiotics, had apparently become endemic. In the second hospital a number of distinct but related strains were present. The isolates were also related but not identical to the strain of MRSA endemic at the London Hospital.

China↗
PubMed1989

Chromosomally-encoded gentamicin resistance in 'epidemic' methicillin-resistant Staphylococcus aureus: detection with a synthetic oligonucleotide probe.

A 30 base synthetic oligonucleotide probe to the AAC(6') coding region of the gentamicin resistance transposon Tn4001 was constructed. This was used to probe plasmid extracts and restriction endonuclease (RE) digests of total DNA from epidemic methicillin-resistant Staphylococcus aureus (EMRSA) isolates. Hybridization occurred to plasmid bands of gentamicin-resistant EMRSA which carry a gentamicin resistance plasmid, but not to DNA of gentamicin-sensitive EMRSA. Hybridization also occurred to RE digestion fragments of total DNA from recently-isolated, plasmid-free gentamicin-resistant EMRSA isolates. This confirmed the presence of the gentamicin-resistance gene in the chromosomal DNA of the 'new' EMRSA isolates.

Acetyltransferases↗
PubMed1989

Cloning and sequence analysis of the 10 kDa antigen gene of Mycobacterium tuberculosis.

The gene encoding a major protein antigen of Mycobacterium tuberculosis has been cloned and sequenced using oligonucleotide probes derived from the N-terminal sequence of the analogous protein from Mycobacterium bovis BCG. The gene analysis revealed a sequence encoding a protein of 99 amino acid residues, with a molecular mass of 10.7 kDa. Computer prediction suggests that the protein contains three T-cell-determined epitopes (of which one has been demonstrated experimentally) and three B-cell-determined epitopes. The protein sequence was homologous to two prokaryote heat-shock proteins and the gene possessed heat-shock-like promoter sequences upstream of the initiation codon. A hairpin loop identified in the upstream sequence may also be important in regulation of the gene.

Antigens, Bacterial↗
PubMed1988

Lactate dehydrogenase isolated from human liver mitochondria: its purification and partial biochemical characterization.

We have demonstrated that lactate dehydrogenase is not solely a cytosolic enzyme by the isolation and purification of the enzyme from the mitochondria of human liver. Treatment of the mitochondria with digitonin reveals the LD activity to be associated with the inner membrane-inner matrix and the outer membrane. The mitochondrial LD consists of two fractions separated by ion exchange and affinity chromatography. The first mitochondrial fraction, LD-Mt1, with isoelectric points of 9.8, 9.6, and 4.8, has subunit components of 14500 and 34000 daltons. The second mitochondrial fraction, LD-Mt2, is similar to cytosolic LD-5 with respect to both isoelectric points and subunit molecular weight. The first mitochondrial fraction, LD-Mt1, has physical characteristics previously associated with the isoenzyme LD-6.

Chromatography, High Pressure Liquid↗
PubMed1988

Characterisation of methicillin-resistant Staphylococcus aureus isolates by restriction endonuclease digestion of chromosomal DNA.

Clinical isolates of Staphylococcus aureus from the London Hospital were characterised by genetic analysis of antibiotic-resistance determinants and by restriction endonuclease digestion of chromosomal DNA and compared with isolates from elsewhere in the UK. Restriction enzyme digestion of chromosomal DNA confirmed that a single strain of methicillin-resistant S. aureus (MRSA) persists at the London Hospital, although its antibiotic-resistance profile and plasmid carriage are not constant. Methicillin-sensitive isolates, on the other hand, each had readily distinguishable and unique DNA restriction patterns. The DNA restriction digest pattern of the London Hospital MRSA isolates was identical to that of "epidemic" (E) MRSA isolates from the Thames regions. By contrast, other MRSA isolates had DNA restriction patterns which differed from those of EMRSA isolates and from each other. These results confirm the discriminatory value of restriction pattern analysis as a typing method.

Chromosomes, Bacterial↗
PubMed1987

Modifiers of position-effect variegation in the region from 86C to 88B of the Drosophila melanogaster third chromosome.

Four dominant suppressor and one enhancer of variegation loci were mapped in the polytene chromosome region extending from section 86C to section 88B of the Drosophila melanogaster third chromosome using a set of deficiencies. The suppressor locus Su-var(3)14 maps in 86CD, Su-var(3)13 in 86F4-7, Su-var(3)6 in 87B4-7 and Su-var(3)7 in 87E4-5. The enhancer locus E-var(3)3 maps in 87E12-F11. Su-var(3)13, Su-var(3)6 and Su-var(3)7 are also defined by point mutant alleles originally identified by other criteria (Reuter et al. 1986). Duplications covering the suppressor loci Su-var(3)14, Su-var(3)13, Su-var(3)6 and Su-var(3)7 were found to reduce considerably the haplo-abnormal effect of heterozygous point mutants of the corresponding loci. One suppressor locus, Su-var(3)7, maps within a region which has previously been cloned. The positions of deficiency breakpoints delimiting the suppressor locus indicate that all the necessary sequences for its function are located within 10 kb of cloned DNA.

Animals↗
PubMed1987

Enhancer of seizure: a new genetic locus in Drosophila melanogaster defined by interactions with temperature-sensitive paralytic mutations.

Mutations in the enhancer of seizure (e(sei] locus have been isolated on the basis of their ability to cause temperature-induced paralysis of alleles at the seizure (sei) locus at temperatures at which these mutations ordinarily do not paralyze. This enhancer is specific to the seizure locus and is without effect on other temperature-sensitive paralytic mutants including para, nap, tip-E and shi. This suggests that the enhancer responds specifically to the mechanism of paralysis mediated by the seizure mutations. The e(sei) is a recessive mutation which maps to 39.0 on the left arm of chromosome 3. Deficiency mapping has placed it at 69A4-B5 on the salivary gland polytene chromosome map. When a new enhancer allele was isolated following P-M hybrid dysgenesis, there was a concomitant P-element insertion at 69B. In the absence of seizure mutations, the enhancer mutation causes non-temperature dependent hyperactivity when agitated and interferes with the climbing response. Electrophysiological studies examined the effects of increasing temperature on electrical activity in the adult giant fiber/flight muscle system. Neuronal hyperactivity was seen in both e(sei) and sei single mutant homozygotes, but not in wild type. The hyperactivity was more severe in the sei;e(sei) double mutants. The correlation between the physiological effects and the mutant behavior suggests that both sei and e(sei) cause membrane excitability defects. Since previous work has shown that seizure mutants affect [3H]saxitoxin binding to the voltage-sensitive sodium channel, e(sei) may code for a gene product which interacts with this channel.

Alleles↗
PubMed1986

The Ace locus of Drosophila melanogaster: structural gene for acetylcholinesterase with an unusual 5' leader.

The Ace locus of Drosophila melanogaster has been mapped at the molecular level. cDNA clones from the locus have been isolated and their sequence determined, confirming that Ace forms the structural gene for acetylcholinesterase (AChE). The cDNAs have a 1950 nucleotide open reading frame from which the complete amino acid sequence of AChE has been deduced. The Drosophila enzyme is found to have extensive homology to the known sequence of Torpedo AChE. Ace cDNAs have an unusual structure with a long 5' leader and several short upstream open reading frames.

Acetylcholinesterase↗
PubMed1986

The tip-E mutation of Drosophila decreases saxitoxin binding and interacts with other mutations affecting nerve membrane excitability.

A recessive temperature-sensitive paralytic mutation, tip-E, is associated with reduced binding of [3H]saxitoxin to voltage-sensitive sodium channels in membranes from adult Drosophila heads. There is a decrease of 30-40% in the number of [3H]saxitoxin-binding sites per mg protein (Bmax), but the dissociation constant (Kd) for [3H]saxitoxin binding is normal in the remaining population of binding sites. This decrease is not due to a general hypotrophy of neural tissue since the number of alpha-bungarotoxin binding sites is normal in tip-E mutants. Although saxitoxin binding is reduced in vitro, pharmacological experiments suggest that tip-E mutants have close to the wild-type number of sodium channels in vivo. This suggestion is supported by the observation that at permissive temperatures tip-E only marginally suppresses a mutation which causes enhanced membrane excitability. However, even at permissive temperatures tip-E interacts synergistically with mutations that decrease membrane excitability. In this case, the double mutants exhibit reduced viability and/or longevity. We postulate that either the structure of sodium channels or their microenvironment is altered in tip-E mutants resulting in an increased liability of binding sites in vitro.

Amphibian Proteins↗
PubMed1985

Rationalization of some genetic anticodonic assignments.

The genetic code appears to be a logic matrix in which, generally speaking, there is a correlation between the hydrophobicities of amino acids and their anticodonic nucleotides. There are several exceptions to this generality, however, and using previous data on hydrophobicity and binding constants, coupled with new data on reaction rates, we rationalize several of the anticodonic assignments.

Amino Acids↗
PubMed1985

Chirally selective, intramolecular interaction observed in an aminoacyl adenylate anhydride.

All earthly creatures use only L-amino acids in template directed protein synthesis. The reason for this exclusive use of the L-isomer is not yet apparent, although recent experiments by Usher and his colleagues have shown some stereoselectivity in the aminoacylation of di- and polynucleotides. We have separately reported on intramolecular interactions between hydrophobic amino acid side chains and the adenine ring in aminoacyl adenylates. There was a preferential association of Phe greater than Leu = Ile greater than Val with the adenine in these studies, but we made no attempts to address the question of D, L selectivity. Recently, in 1H NMR studies of N-acetylphenylalanyl adenylate anhydride, we noticed evidence that both D- and L-isomers of the amino acid were present and, furthermore, that one isomer seemed to be associating with the adenine ring more strongly than the other. Using HPLC, we have separated the two diastereoisomers and have enzymatically determined that the isomer which associates more strongly is the biologically important one, the L-isomer. We present those studies here and discuss the evolutionary significance of this finding.

Adenosine Monophosphate↗
PubMed1985

A human acetylcholinesterase gene identified by homology to the Ace region of Drosophila.

The Ace locus of the Drosophila genome controls biosynthesis of the neurotransmitter-hydrolyzing enzyme acetylcholinesterase (acetylcholine acetylhydrolase, EC 3.1.1.7). We injected the mRNA species hybridizing with DNA fragments from this region into Xenopus oocytes, in which acetylcholinesterase mRNA is translated into active acetylcholinesterase. A 2.0-kilobase (kb) fragment of DNA from this region selectively hybridizes with Drosophila mRNA capable of inducing the biosynthesis of acetylcholinesterase in oocytes. This Drosophila DNA fragment cross-hybridized with human brain poly(A)+ RNA. We therefore used this DNA fragment as a probe for homologous sequence(s) in a human genomic DNA library and thus selected a 13.5-kb human DNA segment. DNA blot-hybridization revealed that a 2.6-kb fragment of this human DNA segment hybridizes with the Drosophila 2.0-kb DNA fragment. Both Drosophila and human fragments hybridized with a human brain mRNA species of about 7.0-kb that was barely detectable in the acetylcholinesterase-deficient HEp carcinoma. A fraction containing mRNA of similar size, extracted from human brain, induced acetylcholinesterase biosynthesis in oocytes. The human DNA fragment also was used in hybridization-selection experiments. In oocytes, hybrid-selected human brain mRNA induced acetylcholinesterase activity that was completely inhibited by 1,5-bis[4-allyldimethylammonium)phenyl]pentan-3-one dibromide but not by tetraisopropyl pyrophosphamide, a differential response to these inhibitors characteristic of "true" human brain acetylcholinesterase. These findings strongly suggest that both the Drosophila and the human DNA fragments are directly involved in controlling acetylcholinesterase biosynthesis.

Acetylcholinesterase↗