scholarly journals Identification of the human mitochondrial S-adenosylmethionine transporter: bacterial expression, reconstitution, functional characterization and tissue distribution

2004 ◽  
Vol 379 (1) ◽  
pp. 183-190 ◽  
Author(s):  
G. AGRIMI ◽  
M. A. Di NOIA ◽  
C. M. T. MAROBBIO ◽  
G. FIERMONTE ◽  
F. M. LASORSA ◽  
...  
Keyword(s):  
Functional Characterization ◽  
Physiological Role ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Bromocresol Purple ◽  
Human Cdna Sequence ◽  
Its Gene ◽  
The Matrix

The mitochondrial carriers are a family of transport proteins that, with a few exceptions, are found in the inner membranes of mitochondria. They shuttle metabolites and cofactors through this membrane, and connect cytoplasmic functions with others in the matrix. SAM (S-adenosylmethionine) has to be transported into the mitochondria where it is converted into S-adenosylhomocysteine in methylation reactions of DNA, RNA and proteins. The transport of SAM has been investigated in rat liver mitochondria, but no protein has ever been associated with this activity. By using information derived from the phylogenetically distant yeast mitochondrial carrier for SAM and from related human expressed sequence tags, a human cDNA sequence was completed. This sequence was overexpressed in bacteria, and its product was purified, reconstituted into phospholipid vesicles and identified from its transport properties as the human mitochondrial SAM carrier (SAMC). Unlike the yeast orthologue, SAMC catalysed virtually only countertransport, exhibited a higher transport affinity for SAM and was strongly inhibited by tannic acid and Bromocresol Purple. SAMC was found to be expressed in all human tissues examined and was localized to the mitochondria. The physiological role of SAMC is probably to exchange cytosolic SAM for mitochondrial S-adenosylhomocysteine. This is the first report describing the identification and characterization of the human SAMC and its gene.

Distribution of protein disulphide isomerase in rat liver mitochondria

2001 ◽  
Vol 356 (2) ◽  
pp. 567-570 ◽  
Author(s):  
Maria Pia RIGOBELLO ◽  
Arianna DONELLA-DEANA ◽  
Luca CESARO ◽  
Alberto BINDOLI
Keyword(s):  
Thioredoxin Reductase ◽  
Immunoblot Analysis ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Specific Marker ◽  
Protein Disulphide Isomerase ◽  
Mitochondrial Functions ◽  
The Matrix ◽  
Molecular Masses

Here we report the localization of protein disulphide isomerase (PDI) in the mitochondrial compartments, comparing it with that of thioredoxin reductase. The latter enzyme is present mostly in the matrix, whereas PDI is located at the level of the outer membrane. We characterize the different submitochondrial fractions with specific marker enzymes. PDI, whether isolated from whole mitochondria or from purified outer membranes, exhibits the same electrophoretic mobility, indicating identical molecular masses. Moreover, immunoblot analysis with monoclonal anti-PDI antibody shows immunoreactivity only with the microsomal PDI, indicating the specificity of the mitochondrial isoform. The significance of these findings is discussed with reference to the potential role of PDI and thioredoxin reductase in regulating the mitochondrial functions dependent on the thiol–disulphide transition.

scholarly journals Mmf1p, a Novel Yeast Mitochondrial Protein Conserved throughout Evolution and Involved in Maintenance of the Mitochondrial Genome

2000 ◽  
Vol 20 (20) ◽  
pp. 7784-7797 ◽  
Author(s):  
Ellinor Oxelmark ◽  
Antonio Marchini ◽  
Ilaria Malanchi ◽  
Francesca Magherini ◽  
Laurence Jaquet ◽  
...  
Keyword(s):  
Mitochondrial Protein ◽  
Liver Mitochondria ◽  
Leader Peptide ◽  
Rat Liver Mitochondria ◽  
Biological Functions ◽  
Direct Role ◽  
The Matrix ◽  
Nonfermentable Carbon Source ◽  
Novel Protein

ABSTRACT A novel protein family (p14.5, or YERO57c/YJGFc) highly conserved throughout evolution has recently been identified. The biological role of these proteins is not yet well characterized. Two members of the p14.5 family are present in the yeast Saccharomyces cerevisiae. In this study, we have characterized some of the biological functions of the two yeast proteins. Mmf1p is a mitochondrial matrix factor, and homologous Mmf1p factor (Hmf1p) copurifies with the soluble cytoplasmic fraction. Δmmf1cells lose mitochondrial DNA (mtDNA) and have a decreased growth rate, while Δhmf1 cells do not display any visible phenotype. Furthermore, we demonstrate by genetic analysis that Mmf1p does not play a direct role in replication and segregation of the mtDNA. rho+ Δmmf1 haploid cells can be obtained when tetrads are directly dissected on medium containing a nonfermentable carbon source. Our data also indicate that Mmf1p and Hmf1p have similar biological functions in different subcellular compartments. Hmf1p, when fused with the Mmf1p leader peptide, is transported into mitochondria and is able to functionally replace Mmf1p. Moreover, we show that homologous mammalian proteins are functionally related to Mmf1p. Human p14.5 localizes in yeast mitochondria and rescues the Δmmf1-associated phenotypes. In addition, fractionation of rat liver mitochondria showed that rat p14.5, like Mmf1p, is a soluble protein of the matrix. Our study identifies a biological function for Mmf1p and furthermore indicates that this function is conserved between members of the p14.5 family.

scholarly journals Characterization of a DNA primase from rat liver mitochondria.

1986 ◽  
Vol 261 (14) ◽  
pp. 6571-6577
Author(s):  
B J Ledwith ◽  
S Manam ◽  
G C Van Tuyle
Keyword(s):  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Dna Primase
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