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G Morelli

Publications and source records attributed to G Morelli.

At least 145 records · Page 8Linked to original sources
PubMed1984

Conservation of plasmids among Escherichia coli K1 isolates of diverse origins.

Escherichia coli K1 isolates of various O types were previously assigned to different clonal groups. Members of the two clones defined by membrane pattern 9 (MP9) and serotypes O18:K1 and O1:K1 had been found to be very similar to each other. The plasmid contents of these bacteria confirmed this conclusion. Both groups carried a self-transmissible plasmid of the FI incompatibility group that coded for colicin production and a major outer membrane protein called the plasmid-coded protein (PCP). The size of this plasmid varied from 76 to 96 megadaltons, but restriction endonuclease digestion and DNA heteroduplex analysis revealed that these plasmids were highly related. O18:K1 bacteria of MP6 had previously been determined to represent a subclone, related to but different from O18:K1 MP9 bacteria. These MP6 bacteria carried a different, smaller IncFI plasmid which did not code for colicin production or the PCP protein. This smaller plasmid was primarily related to the larger plasmid within the regions of DNA encoding incompatibility, replication, and conjugation. O1:K1 bacteria of MP5 contained other unrelated plasmids in agreement with the previous conclusion that they are unrelated to O1:K1 bacteria of MP9. The bacteria examined had been isolated from two continents over a time span of 38 years, and the results attest to conservative inheritance of plasmids within bacteria of common descent.

DNA Restriction Enzymes↗
PubMed1984

Vibrio cholerae bacteriophage CP-T1: characterization of bacteriophage DNA and restriction analysis.

Temperature bacteriophage CP-T1 of Vibrio cholerae has a capsid that is 45 nm in diameter, a contractile tail 65 nm long and 9.5 nm wide, and a baseplate with several spikes or short tail fibers. The linear double-stranded DNA is 43.5 +/- 1.4 kilobases long, and the phage genome is both terminally redundant and partially circularly permuted. The extent of terminal redundancy is ca. 4%, and circular permutation is up to ca. 44%. Circular restriction maps have been constructed for the enzymes HindIII, EcoRI, BamHI, and PstI. By restriction endonuclease and heteroduplex analyses of phage DNA, the presence and location of a site (pac) at which packaging of phage DNA is initiated was established.

Bacteriophages↗
PubMed1983

Cytochrome oxidase subunit 2 gene in Neurospora crassa mitochondria.

The nucleotide sequence of the cytochrome oxidase subunit 2 (COX2) gene has been obtained from cloned mitochondrial DNA segments of Neurospora crassa. The coding sequences have been identified on the basis of protein sequence homology with the subunit 2 of cytochrome oxidase from yeast and man. The postulated precursor of the N. crassa subunit 2 protein is 250 amino acids long, with a molecular weight of 28,700. As in the tRNA and rRNA genes, the subunit 2 gene is flanked by G + C-rich palindromic sequences, which are highly conserved in N. crassa mitochondria. Three major transcripts have been detected by Northern blot hybridization. A transcript of 1100 bases is tentatively considered the fully processed mRNA. Furthermore, S1 nuclease protection experiments have revealed that the putative subunit 2 mRNA has a 330 nucleotide long 5' leader sequence.

Amino Acid Sequence↗
PubMed1983

Nucleotide sequence and intron structure of the apocytochrome b gene of Neurospora crassa mitochondria.

The sequence of the apocytochrome b (cob) gene of Neurospora crassa has been determined. The structural gene is interrupted by two intervening sequences of approximately 1260 bp each. The polypeptide encoded by the exons shows extensive homology with the cob proteins of Aspergillus nidulans and Saccharomyces cerevisiae (79% and 60%, respectively). The two introns are, however, located at sites different from those of introns in the cob genes of A. nidulans and S. cerevisiae (which contain highly homologous introns at the same site within the gene). The introns share several short regions of sequence homology (10-12 bp long) with each other and with other fungal mitochondrial introns. Moreover, the second intron contains a 50 nucleotide long sequence that is highly homologous with sequences within every ribosomal intron of fungal mitochondria sequenced to date. The conserved sequences may allow the formation of a core secondary structure, which is nearly identical in many mitochondrial introns. The conserved secondary structure may be required for intron splicing. The second intron contains an open reading frame, continuous with the preceding exon, of approximately 290 codons. Two stretches of 10 amino acid residues, conserved in many introns, are present in the open reading frame.

Amino Acid Sequence↗
PubMed1983

Statistical and energetic analysis of side-chain conformations in oligopeptides.

The distributions of side-chain conformations in 258 crystal structures of oligopeptides have been analyzed. The sample contains 321 residues having side chains that extend beyond the C beta atom. Statistically observed preferences of side-chain dihedral angles are summarized and correlated with stereochemical and energetic constraints. The distributions are compared with observed distributions in proteins of known X-ray structures and with computed minimum-energy conformations of amino acid derivatives. The distributions are similar in all three sets of data, and they appear to be governed primarily by intraresidue interactions. In side chains with no beta-branching, the most important interactions that determine chi 1 are those between the C gamma H2 group and atoms of the neighboring peptide groups. As a result, the g- conformation (chi 1 congruent to -60 degrees) occurs most frequently for rotation around the C alpha-C beta bond in oligopeptides, followed by the t conformation (chi 1 congruent to 180 degrees), while the g+ conformation (chi 1 congruent to 60 degrees) is least favored. In residues with beta-branching, steric repulsions between the C gamma H2 or C gamma H3 groups and backbone atoms govern the distribution of chi 1. The extended (t) conformation is highly favored for rotation around the C beta-C gamma and C gamma-C delta bonds in unbranched side chains, because the t conformer has a lower energy than the g+ and g- conformers in hydrocarbon chains. This study of the observed side-chain conformations has led to a refinement of one of the energy parameters used in empirical conformational energy computations.

Amino Acids↗
PubMed1983

Streptococcus pneumoniae proteins released into medium upon inhibition of cell wall biosynthesis.

Inhibition of murein biosynthesis in Streptococcus pneumoniae by either penicillin or bacitracin leads to an increase in the amount of protein secreted into the medium. This process was studied in wild-type cells grown under lysis-permissive conditions as well as in an autolysin-deficient mutant. The time course of secretion did not follow cellular lysis but commenced immediately after the addition of the cell wall inhibitor in a manner similar to that described recently for cell wall and membrane components in various tolerant streptococci. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that this increase was not due to the stimulation of release of three protein components which are secreted under normal growth conditions; rather, a complex set of cellular proteins escaped from the antibiotic-treated pneumococci. The proteins released during bacitracin treatment was slightly different from those observed when penicillin was used. Analysis on sucrose gradients indicated that the secreted proteins were membrane bound rather than soluble. Membrane vesicles could indeed be detected by electron microscopy of negative-stained secreted material.

Bacitracin↗
PubMed1982

Analysis of the promoter-distal region of the tra operon of the F sex factor of Escherichia coli K-12 encoded by EcoRI restriction fragments f17, f19, and f2.

The promoter-distal region of the tra operon of the F sex factor Escherichia coli K-12 was analyzed, using the chimeric plasmid pRS31, which contains the F EcoRI restriction fragments f17, f19, and f2 cloned into the EcoRI site of pSC101. A series of deletion plasmids of pRS31, extending increasing distances from a site in f17 through f19 and ending in f2, were isolated. These plasmids were examined by heteroduplex analysis with the parent DNA, and a restriction map of this region of DNA was constructed. A series of Tn5 insertion derivatives of pRS31 were also isolated and mapped, using both heteroduplex analysis and restriction mapping. Both the insertion and deletion mutants were tested in minicells for the synthesis of radioactively labeled proteins. This allowed the identification of the individual gene products and mapping of the genes. The result is a saturated physical map of this region of DNA from fragment f17 through to the IS3 insertion sequence near the promoter-distal end of f2.

Bacterial Proteins↗
PubMed1982

Improvement of the cardiac function after electrical cardioversion of atrial fibrillation. Echocardiographic study in patients with and without mitral stenosis.

The improvement of the cardiac function after electrical cardioversion of atrial fibrillation has been studied by echocardiography by few authors and only in patients without mitral stenosis. Moreover, discordant results have been obtained. We have studied nine patients with mitral valve disease as well as nine other patients with ischemic heart disease. Both groups were cardioverted within five days of onset of atrial fibrillation, and appropriate echocardiographic measurements were made one hour before and two hours after cardioversion. We found a significant decrease of left atrial diameter in both groups, as well as a significant increase of the end-diastolic diameter and volume of left ventricle and an improvement of the cardiac index. These changes were significantly more pronounced in patients with mitral valve disease and they appear in accordance with the improvement of the cardiac function demonstrated with invasive hemodynamic studies after cardioversion to sinus rhythm. In the group of patients with mitral valve disease and a very dilated left atrium (more than 6 cm. of diameter) atrial fibrillation recurred within the next twelve months. In spite of the limitations of M-mode approach for calculating left ventricular volumes, echocardiography appears to be sensitive and useful for evaluating in the single patient the changes in left ventricular performance after cardioversion of atrial fibrillation to sinus rhythm.

Arteriosclerosis↗
PubMed1981

Cloning and expression of the Bacillus subtilis phage SPP1 in E. coli. I. Construction and characterization of lambda/SPP1 hybrids.

We have constructed lambda/SPP1 hybrid phages by in vitro ligation of EcoRI fragments of the Bacillus subtilis phage SPP1 DNA to a lambdoid bacteriophage vector. EcoRI digestion of SPP1 generated 15 DNA fragments of which 13 could be cloned. The SPP1 DNA of such hybrids was stably maintained and replicated in Escherichia coli, as indicated by marker rescue experiments in B. subtilis. EcoRI fragment 1 of SPP1 could not be cloned although subfragments of fragment 1 resulting from spontaneous deletions which occurred during the cloning regime were consistently obtained. A region within EcoRI fragment 1 responsible for its incompatibility with replication in E. coli was defined by these experiments.

Bacillus subtilis↗
PubMed1981

Promoter sites in the genome of B. subtilis phage SPP1.

Transcriptional complexes formed in vitro using DNA of B. subtilis phage SPP1 as template and E. coli and B. subtilis RNA polymerases were analyzed by electron microscopy. Both enzymes recognize the same five strong promoters in the early region of the genome. Strand selection at these sites was identical with both enzymes. These results correlate well with data obtained from in vivo transcription studies. Transcriptional activity in the late region of the genome was very low, not permitting the identification of promoter sites.

Bacillus subtilis↗
PubMed1981

traG protein of the F sex factor of Escherichia coli K-12 and its role in conjugation.

The traG protein of the F sex factor is an inner membrane protein with a molecular weight of 116,000. Mutants in traG (or in traN) are able to trigger conjugal DNA replication even though they cannot efficiently form stable mating aggregates with F(-) cells. The traG protein (and the traN protein) probably acts in the donor at the stabilization stage of conjugation.

Bacterial Proteins↗
PubMed1979

Different specific activities of the monomeric and oligomeric forms of plasmid DNA in transformation of B. subtilis and E. coli.

(1) The low residual transforming activity in preparations of monomeric, supercoiled, circular (CCC) forms of the plasmids pC194 and pHV14 could be attributed to the presence in such isolates of a small number of contaminating multimeric molecules. (2) E. coli derived preparations of pHV14, as in vitro recombinant plasmid capable of replication in both E. coli and B. subtilis, contain oligomeric forms of plasmid DNA in addition to the prevalent monomeric CCC form. The specific transforming activity of pHV14 DNA for E. coli is independent of the degree of oligomerization, whereas in transformation of B. subtilis the specific activity of the purified monomeric CCC molecules is at least four orders of magnitude less than that of the unfractionated preparation. (3) Oligomerization of linearized pHV14 DNA by T4 ligase results in a substantial increase of specific transforming activity when assayed with B. subtilis and causes a decrease when used to transform E. coli.

Bacillus subtilis↗