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E Ricca

Publications and source records attributed to E Ricca.

At least 37 records · Page 2Linked to original sources
PubMed1994

[Hypercalcitoninemia and disorders of dentition development. A family study].

INTRODUCTION: A lot of factors interfere in the physiopathology of the exfoliation of the primary teeth. One of the most important factors is bone shuffle which is due to osteoclastic activity; this activity is controlled by a hormonal equilibrium. CLINICAL CASE: The aim of the present study was to correlate primary teeth's exfoliation delay in two brothers with their hypercalcitoninemia. They had a positive familiar anamnesis for thyroid medullar cancer; this disease is notoriously associated with hypercalcitoninemia. CONCLUSIONS: The connection between a high basal and after-stimulation seric level of calcitonin and a lower activity of osteoclasis is evident. Thus, i also appeared evident to us the connection between the hormonal disease of the two children and the delay of exfoliation of their primary teeth. In these cases, it is important to control periodically the patients in order to prevent or to diagnose early isolated medullar thyroid cancer or a multiple endocrine adenomatosis.

Adolescent↗
PubMed1993

A stereospecific alignment between the promoter and the cis-acting sequence is required for Lrp-dependent activation of ilvIH transcription in Escherichia coli.

The leucine-responsive regulatory protein (Lrp) is a DNA binding protein that affects, either positively or negatively, the expression of several E. coli genes. The ilvIH operon is positively regulated by Lrp and leucine counteracts this effect reducing 5- to 10-fold the efficiency of ilvIH transcription. An investigation of the mechanism of transcription activation of the ilvIH operon by Lrp indicated that: (i) a stereospecific alignment between the ilvIH promoter and the cis-acting sequence upstream of it is required for activation; (ii) a correct distance between the promoter and the adjacent cis-acting sequence is needed for leucine to counteract the positive role of Lrp; (iii) Lrp fails to activate transcription when the cis-acting region is placed several hundred base pairs upstream of the ilvIH promoter.

Bacterial Proteins↗
PubMed1993

Acetohydroxy acid synthase and threonine deaminase activities, and the biosynthesis of isoleucine-leucine-valine in Streptococcus bovis.

Acetohydroxy acid synthase (AHAS) and threonine deaminase (TD) activities were found in Streptococcus bovis and shown to be involved in the biosynthesis of the branched chain amino acids isoleucine, leucine and valine. Apparent lack of repression of AHAS synthesis by the end-products and reduced sensitivity of S. bovis growth to analogues of the branched chain amino acids suggested that secretion of isoleucine, leucine and valine in the growth medium may be a consequence of the regulatory features of AHAS. A glycyl-leucine-resistant mutant with reduced TD activity secreted a reduced amount of isoleucine and an increased amount of valine, which might be a result of the reduced rate of synthesis of the isoleucine precursor alpha-ketobutyrate and of a consequent preferential carbon flow through the valine branch of the pathway.

Acetolactate Synthase↗
PubMed1993

Organization of Lrp-binding sites upstream of ilvIH in Salmonella typhimurium.

Lrp, a major regulatory protein in Escherichia coli, controls the expression of numerous operons, including ilvIH. Lrp binds to six sites upstream of ilvIH, and Lrp binding is required for ilvIH expression. We show here that an Lrp-like protein is also present in Salmonella typhimurium. This protein can bind both E. coli and S. typhimurium ilvIH DNA, as can E. coli Lrp. Methidiumpropyl-EDTA footprinting studies were performed with purified E. coli Lrp and S. typhimurium ilvIH DNA. Six binding sites were defined, three of them being similar to corresponding sites in E. coli, and three being organized differently. A consensus derived from six S. typhimurium sites is compatible with that derived from a similar analysis of E. coli sequences.

Acetolactate Synthase↗
PubMed1993

An unusually small gene required for sporulation by Bacillus subtilis.

We report the cloning and characterization of an unusually small gene called spoVM whose product is required for normal formation of the cortex and coat during sporulation in Bacillus subtilis. The spoVM gene is adjacent to, and in convergent orientation with, the B. subtilis homologue to the Escherichia coli gene for ribosomal protein L28. The spoVM open reading frame is only 26 codons in length and is capable of encoding a polypeptide of 3 kDa. The short length of spoVM was verified by means of complementation experiments with wild-type and deletion-mutated copies of the open reading frame and by engineering the synthesis of the spoVM gene product in E. coli. Transcription of spoVM was induced during the second hour of sporulation (approximately stage II) by the appearance of the sporulation RNA polymerase sigma factor, sigma E. Efficient transcription of spoVM additionally required the action of the sporulation DNA-binding protein SpoIIID. Because spoVM was not strongly required for the transcription of several genes expressed at late times in development, its protein product is likely to play a morphogenetic rather than a regulatory role in sporulation.

Amino Acid Sequence↗
PubMed1993

Antimicrobial activity of a newly identified bacteriocin of Bacillus cereus.

A bacteriocin-producing Bacillus cereus strain was isolated. The bacteriocin, here called cerein, was shown to be active specifically against other B. cereus strains and inactive against all other bacterial species tested. Cerein was detected in the culture supernatants of stationary-phase cells, and its appearance was inhibited by induction of sporulation. The bacterial activity of cerein was insensitive to organic solvents and nonproteolytic enzymes, partially stable to heat, and active over a wide range of pH values. Direct detection of antimicrobial activity on sodium dodecyl sulfate-polyacrylamide gel suggested an apparent molecular mass of about 9 kDa.

Bacillus cereus↗
PubMed1993

Identification and characterization of the proBA operon of Streptococcus bovis.

A genomic DNA library of the rumen bacterium Streptococcus bovis was constructed in Escherichia coli, and recombinant plasmids able to complement proA and proB mutations of the host were found. Southern hybridization and restriction analysis showed that a 3.5-kb fragment of S. bovis DNA contained two genes, organized in an operon and coding for enzymes functionally similar to the glutamyl phosphate reductase-glutamyl kinase enzyme complex that in E. coli catalyzes the first step of proline biosynthesis. Complementation of the E. coli mutations was observed with the fragment inserted in both orientations, which suggested that the S. bovis proBA operon was transcribed from its own promoter. Genetic and biochemical data suggested that the proline biosynthetic pathway of S. bovis is similar to the one previously characterized for E. coli.

DNA, Bacterial↗
PubMed1992

Characterization of bofA, a gene involved in intercompartmental regulation of pro-sigma K processing during sporulation in Bacillus subtilis.

Sporulating cells of the gram-positive bacterium Bacillus subtilis are partitioned into two cellular compartments called the mother cell and the forespore. Gene expression in the mother cell and the forespore is regulated differentially by the compartment-specific transcription factors sigma K and sigma G, respectively. Gene expression between the two compartments is also coordinated by a signal transduction pathway that couples the activation of sigma K (by processing of its inactive precursor pro-sigma K) in the mother cell to sigma G-directed gene expression in the forespore. To dissect the signal transduction pathway genetically, we previously isolated bypass of forespore mutations at loci called bofA and bofB that relieve the dependence of pro-sigma K processing on the action of sigma G. bofB mutations were previously shown to be allelic to the two-cistron sporulation operon spoIVF, which encodes the pro-sigma K-processing enzyme or its regulator. We now report that bofA mutations are located in a small open reading frame of 87 codons that encodes a putative integral membrane protein with three potential membrane-spanning domains. The possibility is discussed that BofA and the SpoIVF proteins form a heteromeric complex in the mother cell membrane that surrounds the forespore and that this complex mediates the intercompartmental coupling of pro-sigma K processing to events in the forespore.

Amino Acid Sequence↗
PubMed1991

Absence of acetohydroxy acid synthase III in Salmonella typhimurium is due to early termination of translation within the ilvl gene.

The cryptic ilvlH locus of Salmonella typhimurium has genetic information for two distinct subunits of acetohydroxy acid synthase III. We show that the ilvH-encoded subunit is normally translated and the lack of activity is due to early termination of translation within the promoter-proximal ilvl gene. Analysis of the 5' region of the operon led to identification of the promoter and the amino-terminal part of ilvl. Expression of this gene in a mutant producing acetohydroxy acid synthase is due to a transversion which creates a UUA (leucine) codon in the place of a UGA (stop) codon present in position 12 of the wild-type coding region.

Acetolactate Synthase↗
PubMed1989

A protein that binds to the regulatory region of the Escherichia coli ilvIH operon.

The ilvIH operon of Escherichia coli encodes acetohydroxyacid synthase III, an isoenzyme involved in branched-chain amino acid biosynthesis. Transcription of the ilvIH operon is repressed by growing cells in the presence of leucine (C.H. Squires, M. DeFelice, S.R. Wessler, and J.M. Calvo, J. Bacteriol. 147:797-804, 1981). A protein in crude extracts of E. coli, termed the ilvIH-binding (IHB) protein, bound specifically in vitro to DNA upstream of the ilvIH operon. The binding protein, partially purified by Polymin precipitation, gel filtration, and phosphocellulose chromatography, has a native molecular weight of 43,000 and is composed of two subunits of identical size. As determined by protection against lambda exonuclease and DNase I, the protein binds within a region -190 to -260 relative to the start point of transcription. In addition, the IHB protein binds to a site between positions -100 and -40. The following evidence suggests that binding of this protein to the region upstream of ilvIH is related to the regulation of this operon by leucine. Binding of the IHB protein to the ilvIH regulatory region in vitro was reduced by leucine but not by isoleucine, valine, or threonine. In a mutant strain isolated by M.V. Ursini, P. Arcari, and M. DeFelice (Mol. Gen. Genet. 181:491-496, 1981), transcription was not repressed by leucine. A protein in extracts of this mutant strain bound to the ilvIH regulatory region, but the complex migrated through agarose gels with a mobility different from that of the complex formed by wild-type protein. Furthermore, a concentration of leucine that substantially reduced binding of the wild-type to DNA did not affect binding of the protein from the mutant strain. A simple model consistent with these findings is that transcription from the ilvIH promoter is stimulated by binding the IHB protein to one or more sites upstream of the promoter and that leucine interferes with this binding.

Acetolactate Synthase↗
PubMed1988

Enhanced acetohydroxy acid synthase III activity in an ilvH mutant of Escherichia coli K-12.

The acetohydroxy acid synthase III isozyme, which catalyzes the first common step in the biosynthesis of isoleucine, leucine, and valine in Escherichia coli K-12, is composed of two subunits, the ilvI and ilvH gene products. A missense mutation in ilvH (ilvH612), which reduced the sensitivity of the enzyme to the end product inhibition by valine, also increased its specific activity and lowered the Km for alpha-acetolactate synthesis. The mutation increased the sensitivity of acetohydroxy acid synthase III to dialysis and heat treatment and reduced the requirement for thiamine pyrophosphate addition to the assay mixture for activity. A strain carrying the ilvH612 mutation grew better than a homologous ilvH+ strain in the presence of leucine. The data indicate that this is a consequence of a more active acetohydroxy acid synthase III isozyme rather than the result of an alteration of the leucine-mediated repression of the ilvIH operon.

Acetolactate Synthase↗