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V Iacobazzi

Publications and source records attributed to V Iacobazzi.

31 records · Page 2Linked to original sources
PubMed1994

The sequences of human and bovine genes of the phosphate carrier from mitochondria contain evidence of alternatively spliced forms.

The sequences of the human and bovine genes for the phosphate carrier from the inner membranes of mitochondria have been determined. The genes have similar structures and each is divided into nine exons. In both genes, two exons, named IIIA and IIIB, are closely related, and they appear to the alternatively spliced. The human exon IIIB sequence is found in a published human heart cDNA sequence, and bovine exon IIIA forms part of a published bovine heart cDNA sequence. By further examination of the human heart cDNA library, sequences arising from both alternatively spliced forms of the phosphate carrier have been characterized. Both forms were also found in several bovine tissues, but the ratios of expression of the two forms varied. The form containing exon IIIA was expressed most highly in bovine heart and liver, less highly in brain and kidney, and only in low amounts in lung. The opposite hierarchy was found for the form containing exon IIIB; it was most highly expressed in lung and least in heart and liver. The alternative splicing mechanism affects amino acids 4-45 of the mature phosphate carrier protein, which is believed to form one of six transmembrane segments of the phosphate carrier and to emerge into a large extramembranous loop. The alternative splicing mechanism changes 13 and 11 amino acids in the human and bovine carrier proteins, respectively. As the function of this region of the phosphate carrier is not known, the effects of the changes on carrier function are not understood at present.

Alternative Splicing↗
PubMed1993

Transmembrane topology, genes, and biogenesis of the mitochondrial phosphate and oxoglutarate carriers.

Phosphate and oxoglutarate carriers transport phosphate and oxoglutarate across the inner membranes of mitochondria in exchange for OH- and malate, respectively. Both carriers belong to the mitochondrial carrier protein family, characterized by a tripartite structure made up of related sequences about 100 amino acids in length. The results obtained on the topology of the phosphate and oxoglutarate carriers are consistent with the six alpha-helix model proposed by Saraste and Walker. In both carriers the N- and C-terminal regions are exposed toward the cytosol. In addition, the oxoglutarate carrier has been shown to be a dimer by means of crosslinking studies. The bovine and human genes coding for the oxoglutarate carrier are split into eight and six exons, respectively, and five introns are found to the same position in both genes. The bovine and human phosphate carrier genes have the same organization with nine exons separated by eight introns at exactly the same positions. The phosphate carrier of mammalian mitochondria is synthesized with a cleavable presequence, in contrast to the oxoglutarate carrier and the other members of the mitochondrial carrier family. The precursor of the phosphate carrier is efficiently imported, proteolytically processed, and correctly assembled in isolated mitochondria. The presequence-deficient phosphate carrier is imported with an efficiency of about 50% as compared with the precursor of the phosphate carrier and is correctly assembled, demonstrating that the mature portion of the phosphate carrier contains sufficient information for import and assembly into mitochondria.

Amino Acid Sequence↗
PubMed1992

Sequences of the human and bovine genes for the mitochondrial 2-oxoglutarate carrier.

The oxoglutarate carrier transports 2-oxoglutarate across the inner membranes of mitochondria in an electroneutral exchange for malate or other dicarboxylic acids. The sequences of its human and bovine genes have been determined from overlapping genomic clones generated by polymerase chain reactions by use of primers and probes based on the bovine cDNA sequence. The bovine and human genes are split into 6 and 8 exons, respectively, and five introns are found in the same positions in both genes. The coding and protein sequences are 93% and 96.6% identical, respectively. The human oxoglutarate carrier protein is 314 amino acids in length and, in common with the bovine protein, does not appear to have a processed presequence to help to target it into mitochondria.

Amino Acid Sequence↗
PubMed1990

Sequence of the bovine 2-oxoglutarate/malate carrier protein: structural relationship to other mitochondrial transport proteins.

The amino acid sequence of the 2-oxoglutarate/malate carrier protein, a component of the inner membranes of mitochondria, has been deduced from the sequences of overlapping cDNA clones. These clones were generated in polymerase chain reactions using, in the first instance, complex mixtures of oligonucleotides as primers and probes, with sequences based upon partial protein sequences of cyanogen bromide fragments of the purified protein. The protein sequence of the carrier, including the initiator methionine, is 314 amino acids long. The mature protein has a modified alpha-amino group, but the nature of this modification and the precise position of the mature N-terminal amino acid have not been ascertained, although it must lie in amino acids 1-4 of the deduced protein sequence. Comparison of the protein sequence with itself and with those of 3 other mitochondrial carrier proteins, ADP/ATP translocase, the phosphate carrier, and the uncoupling protein from brown fat, shows that all 4 proteins contain a 3-fold repeated sequence about 100 amino acids in length, and all the repeats are interrelated. This suggests that the members of this family of proteins have similar structures and mechanisms and that they have evolved from a common origin. The distribution of hydrophobic amino acids in the oxoglutarate/malate carrier supports the view that the domains are folded into similar structural motifs, possibly consisting of two transmembrane alpha-helices joined by an extensive extramembranous hydrophilic region. Clones of cDNA arising from a longer related transcript of the oxoglutarate/malate carrier gene have also been analyzed. They contain 271 additional nucleotides in the 3' noncoding region.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1990

The epsilon-subunit of ATP synthase from bovine heart mitochondria. Complementary DNA sequence, expression in bovine tissues and evidence of homologous sequences in man and rat.

The epsilon-subunit of ATP synthase from bovine heart mitochondria is assembled into the extrinsic membrane sector, F1-ATPase. The mature protein is 50 amino acid residues in length and its function is unknown. It is a nuclear gene product that is imported into the organelle. A mixture of 64 oligonucleotides 17 bases long, designed on the basis of the known protein sequence, was synthesized and used as a hybridization probe to isolate a cognate cDNA clone from a bovine library. The DNA sequence of this clone was determined, and the protein sequence of the epsilon-subunit deduced from it agrees exactly with that determined by direct sequence analysis of the protein isolated from bovine hearts. The bovine cDNA was used as a hybridization probe to examine the expression of the epsilon-subunit in various bovine tissues. mRNAs related to the cDNA are found in all of these tissues, and no evidence was obtained of the presence of mRNAs for the epsilon-subunit with similar coding sequences and dissimilar 3' non-coding regions. By hybridization experiments with digests of DNA from cow, man and rat it has been shown that sequences related to the bovine cDNA are present in the genomes of all three species. More than one related sequence was detected in all cases, indicating the presence in all three genomes of more than one gene and/or pseudogenes.

Amino Acid Sequence↗
PubMed1979

The transport of L-cysteinesulfinate in rat liver mitochondria.

1. The mechanism of L-cysteinesulfinate permeation into rat liver mitochondria has been investigated. 2. Mitochondria do not swell in ammonium or potassium salts of L-cysteinesulfinate in all the conditions tested, including the presence of valinomycin and/or carbonylcyanide p-trifluoromethoxyphenylhydrazone. 3. The activation of malate oxidation by L-cysteinesulfinate is abolished by aminooxyacetate, an inhibitor of the intramitochondrial aspartate aminotransferase, it is not inhibited by high concentrations of carbonylcyanide p-trifluoromethoxyphenylhydrazone (in contrast to the oxidation of malate plus glutamate) and it is decreased on lowering the pH of the medium. 4. All the aspartate formed during the oxidation of malate plus L-cysteinesulfinate is exported into the extramitochondrial space. 5. Homocysteinesulfinate, cysteate and homocysteate, which are all good substrates of the mitochondrial aspartate aminotransferase, are unable to activate the oxidation of malate. Homocysteinesulfinate and homocysteate have no inhibitory effect on the L-cysteinesulfinate-induced respiration, whereas cysteate inhibits it competitively with respect to L-cysteinesulfinate. 6. In contrast to D-aspartate, D-cysteinesulfinate and D-glutamate, L-aspartate inhibits the oxidation of malate plus L-cysteinesulfinate in a competitive way with respect to L-cysteinesulfinate. Vice versa, L-cysteinesulfinate inhibits the influx of L-aspartate. 7. Externally added L-cysteinesulfinate elicits efflux of intramitochondrial L-aspartate or L-glutamate. The cysteinesulfinate analogues homocysteinesulfinate, cysteate and homocysteate and the D-stereoisomers of cysteinesulfinate, aspartate and glutamate do not cause a significant release of internal glutamate or aspartate, indicating a high degree of specificity of the exchange reactions. External L-cysteinesulfinate does not cause efflux of intramitochondrial Pi, malate, malonate, citrate, oxoglutarate, pyruvate or ADP. The L-cysteinesulfinate-aspartate and L-cysteinesulfinate-glutamate exchanges are inhibited by glisoxepide and by known substrates of the glutamate-aspartate carrier. 8. The exchange between external L-cysteinesulfinate and intramitochondrial glutamate is accompanied by translocation of protons across the mitochondrial membrane in the same direction as glutamate. The L-cysteinesulfinate-aspartate exchange, on the other hand, is not accompanied by H+ translocation. 9. The ratios delta H+/delta glutamate, delta L-cysteinesulfinate/delta glutamate and delta L-cysteinesulfinate/delta aspartate are close to unity. 10. It is concluded that L-cysteinesulfinate is transported by the glutamate-aspartate carrier of rat liver mitochondria. The present data suggest that the dissociated form of L-cysteinesulfinate exchanges with H+-compensated glutamate or with negatively charged aspartate.

Animals↗
PubMedDate not supplied

Aberrant mRNA splicing associated with coding region mutations in children with carnitine-acylcarnitine translocase deficiency.

This report describes three infants with genetic defects of carnitine-acylcarnitine translocase (CACT), an inner mitochondrial membrane carrier that is essential for long-chain fatty acid oxidation. Two of the patients were of European and Chinese origin; the third was from consanguineous Turkish parents. CACT activity was totally deficient in cultured skin fibroblasts from all three patients. Patient 1 was heterozygous for a paternal frameshift mutation (120 del T in exon 1) and a maternal lariat branch point mutation (-10 T --> G in intron 2). Patient 2 was heterozygous for the same lariat branch point (-10T --> G intron 2) mutation, derived from the father, and a maternal frameshift mutation (362 del G in exon 3). Patient 3 was homozygous for a frameshift mutation (306 del C in exon 3). All of the three frameshift mutations give rise to the same stop codon at amino acid residue 127 which is predicted to cause premature protein truncation. In addition, cDNA transcript analysis showed that these coding sequence mutations also increase the amount of aberrant mRNA splicing and exon skipping at distances up to 7.7 kb nucleotides from mutation sites. The data suggest that the stability of mRNA transcripts is decreased or the frequency of aberrant splicing is increased in the presence of CACT coding sequence mutations. These results confirm that CACT is the genetic locus of the recessive mutations responsible for the fatal defects of fatty acid metabolism previously associated with deficiency of translocase activity in these three cases.

Carnitine Acyltransferases↗