Effects of cycloleucine on mitochondrial RNA

Identification and functional reconstitution of yeast mitochondrial carrier for S-adenosylmethionine

“…In Saccharomyces cerevisiae , S ‐adenosylmethionine (SAM) is synthesized from ATP and methionine by two synthetases, Sam1p (Thomas and Surdin‐Kerjan, 1987) and Sam2p (Thomas and Surdin‐Kerjan, 1991), that are both localized exclusively in the cytosol (Kumar et al ., 2002). SAM has therefore to be imported into the mitochondria, where it is required as a methyl group donor for DNA, RNA and protein methylation (Gantt and Schneider, 1979; Dubin et al ., 1982; Pintard et al ., 2002; Santamaria et al ., 2003), for sterol methylation (McCammon et al ., 1984) and as essential cofactor in the last step of biotin and lipoic acid biosyntheses catalyzed by biotin synthetase (Bio2p) and lipoate synthetase (Lip5p), respectively (Sulo and Martin, 1993; Zhang et al ., 1994; Marquet et al ., 2001; Kumar et al ., 2002).…”

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

“…SAM is in fact essential for the methylation of various types of nucleic acid present in the mitochondria. In mammals, several methylations of DNA [1][2][3][4], transfer RNA [6][7][8][9][10] and rRNA [11][12][13][14] have been identified, and some of them have been shown to be essential for function [6,7,16,17]. Besides being crucial for mitochondrial protein synthesis, SAM is necessary for post-translational modifications of some mitochondrial proteins.…”

“…In mitochondria, it is required for the methylation of DNA, RNA and proteins [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] and as an intermediate in the biosynthesis of lipoic acid [21,22], ubiquinone [23,24] and, in yeast, biotin [25,26]. Since mitochondria have a relatively large pool of SAM [27] and the enzyme necessary for its synthesis, methionine adenosyltransferase, is present in the cytosol and not in the mitochondria (see [28] and references therein), it was hypothesized that a carrier-mediated system is responsible for the transport of SAM from the cytosol into the mitochondria.…”

“…By using a Saccharomyces cerevisiae protein, Sam5p (S. cerevisiae SAMC protein), which has very recently been shown in our laboratory to be a SAM transporter [29], human ESTs (expressed sequence tags) were identified that encode Abbreviations used: BFP, blue fluorescent protein; CAC, carnitine-acylcarnitine carrier; CHO, Chinese-hamster ovary; EST, expressed sequence tag; GFP, green fluorescent protein; EGFP, enhanced green fluorescent protein; SAC, S-adenosylcysteine; SAHC, S-adenosylhomocysteine; SAM, S-adenosylmethionine; SAMC, S-adenosylmethionine carrier; Sam5p, Saccharomyces cerevisiae SAMC protein. 1 To whom correspondence should be addressed (e-mail fpalm@farmbiol.uniba.it). The nucleotide sequence data reported for SAMC will appear in the DDBJ, EMBL, GenBank ® and GSDB Nucleotide Sequence Databases under the accession number AJ580932.…”