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M T Carri

Publications and source records attributed to M T Carri.

9 recordsLinked to original sources
PubMed1998

Voltage-activated sodium currents in a cell line expressing a Cu,Zn superoxide dismutase typical of familial ALS.

The whole-cell configuration of the patch-clamp recording was used to study the voltage-dependent Na+ currents in a model system for the familial form of amyotrophic lateral sclerosis (ALS) associated with mutations in Cu,Zn superoxide dismutase. Here we report that the amplitude of voltage-gated Na+ currents is significantly reduced in cell lines expressing mutant Cu,Zn superoxide dismutase G93A when compared with the parental, untransfected cell line and to a cell line expressing the wild-type enzyme. This effect is associated with a shift toward positive values of the steady-state inactivation curve of the Na+ currents. These results indicate that expression of a Cu,Zn superoxide dismutase typical of patients affect with familial ALS influence the functionality of the voltage-dependent Na+ channels; this effect may contribute to the pathogenesis of the disease.

4-Aminopyridine↗
PubMed1994

Impaired copper binding by the H46R mutant of human Cu,Zn superoxide dismutase, involved in amyotrophic lateral sclerosis.

Several point mutations in the gene coding for human Cu,Zn superoxide dismutase have been reported as being responsible for familial amyotrophic lateral sclerosis (FALS). However, no direct demonstration has been provided for a correlation between total superoxide dismutase activity and severity of the FALS pathology. In order to get a better insight into the mechanism(s) underlying the FALS phenotype, we have investigated the activity and the copper binding properties of the single mutant H46R, which is associated with a Japanese form of FALS. We have shown that this mutant is structurally stable but lacks significant enzyme activity and has impaired capability of binding catalytic copper. The mutant protein can be fully reconstituted with copper in vitro but its ESR spectrum displays an axial shape quite different from that of the wild-type.

Amyotrophic Lateral Sclerosis↗
PubMed1994

Crystal structure of the cyanide-inhibited Xenopus laevis Cu,Zn superoxide dismutase at 98 K.

The crystal structure of cyanide-inhibited X. laevis Cu,Zn superoxide dismutase has been studied and refined based on diffraction data collected at 98 K. The final R-factor for the 27,299 reflections in the 10.0-1.7 A resolution range is 0.170. The cyanide anion, which is a competitive inhibitor expected to mimic the superoxide binding mode, binds directly to the active site copper atom, replacing the coordinated water molecule. Moreover, the anion establishes a strong electrostatic interaction with the guanidinium group of the conserved active site residue Arg141. The coordination sphere of Cu2+ is partly altered with respect to the uninhibited enzyme: a displacement of 0.41 A in subunit A, and 0.27 A in subunit B of the dimeric enzyme is observed for the Cu2+ ions. Only two ligands in the Cu2+ coordination sphere (His46 and His118) are significantly affected by cyanide binding, whereas virtually no rearrangement of the Zn2+ ligands is reported.

Animals↗
PubMed1993

Chaperonins dependent increase of Cu,Zn superoxide dismutase production in Escherichia coli.

Over-expression of the chaperonins GroEL and GroES significantly suppressed the temperature-dependent pattern of expression of Cu,Zn superoxide dismutases in Escherichia coli and increased the yield of active enzyme. The results obtained indicate that chaperonins prevent degradation of metal-deficient enzyme molecules. GroEL was shown to form a complex with unfolded Cu,Zn superoxide dismutase in vitro, confirming that GroEL can interact with beta-stranded proteins.

Animals↗
PubMed1991

Evidence for co-regulation of Cu,Zn superoxide dismutase and metallothionein gene expression in yeast through transcriptional control by copper via the ACE 1 factor.

Saccharomyces cerevisiae mutant strain DTY26, lacking ACE1, the protein mediator for the induction of metallothionein gene expression, is unable to increase Cu,Zn superoxide dismutase mRNA in response to copper. In the wild-type strain DTY22 transcription of both Cu,Zn superoxide dismutase and metallothionein genes is induced by copper and silver, as expected on the basis of previous results indicating that ACE1 binds only Ag(I) besides Cu(I). We conclude that at the transcriptional level Cu,ZnSOD is co-regulated with metallothionein. Furthermore, structural similarities between the two promoters were found, which could explain the co-regulation effect and the quantitative differences in the response of the two genes to copper.

Base Sequence↗
PubMed1990

The Cu,Zn superoxide dismutase isoenzymes of Xenopus laevis: purification, identification of a heterodimer and differential heat sensitivity.

The three Cu,Zn superoxide dismutase electromorphs of the amphibian Xenopus laevis were purified by an original procedure. N-terminal sequence analysis demonstrated that they are two different homodimers (AA and BB) and a hybrid heterodimer (AB), arising from the co-expression of duplicated genes. The three forms have the same pI, same enzyme activity and EPR spectra, but different heat-sensitivity, form BB being more resistant than form AA, with form AB showing intermediate sensitivity. Thermostability of BB and the control bovine enzyme was enhanced by a tenfold increase in protein concentration. It is suggested that the higher heat sensitivity of the AA isoenzyme is related to the presence of an extra Cys residue and to an easier dissociation of the protein dimer into monomers.

Amino Acid Sequence↗
PubMed1984

Xenopus laevis U1 snRNA genes: characterisation of transcriptionally active genes reveals major and minor repeated gene families.

Xenopus laevis U1 snRNA genes are found in several different genomic arrangements. The major family of genes is organised in tandem repeats of 1.8 kb. The minor U1-family is much less abundant and is present on 1.2-kb HinfI restriction fragments. In addition there are genomic arrangements present in one or very few copies, which could represent the ends of repeating units. There is no evidence for the presence of U1 pseudogenes in Xenopus. A cluster of U1 snRNA genes consisting of a member of the minor class of U1 snRNA genes and two of the 'rarely represented' genes was cloned. All three genes were expressed upon microinjection into frog oocytes. A fragment containing 149 bp of 5' flanking sequence, the RNA coding sequence, and 27 bp of 3' flanking sequence was shown to be accurately transcribed into U1 snRNA. These oocyte transcripts are assembled into specific U1 snRNPs. Sequence comparison of the regions flanking Xenopus U1 and U2 snRNA genes showed the presence of two blocks of homology, which are also conserved in many other U snRNA genes. One of these blocks is found at position -60 to -50 before the coding sequence, and we discuss its possible role in the correct initiation of transcription. The other is 3' to the coding sequence and may be involved in the accurate production of mature 3' ends in the RNA.

Animals↗