title: Transport of S-adenosylmethionine in Saccharomyces cerevisiae.
abstract: The properties of a specific system for the transport of S-adenosylmethionine in yeast are described. The process was pH-, temperature-, and energy-dependent, and showed saturation kinetics. The K(m) for the system was 3.3 x 10(-6)m. Of the S-adenosylmethionine moieties tested, only S-adenosylhomocysteine competitively inhibited the uptake of the adenosylsulfonium compound. Adenine, adenosine, methionine, homocysteine, and the sulfonium compound S-methylmethionine were without effect. The analogue S-adenosylethionine showed competitive inhibition. Under conditions of inhibition of protein synthesis by cycloheximide or methionine starvation, permease activity was stable. The mutant sam-p3 apparently was able to transport S-adenosylmethionine only by diffusion. Uptake by diploids containing this mutation was directly proportional to the gene dose.
mesh_terms: D000241:Adenosine / Q000378:metabolism*; D001386:Azides / Q000494:pharmacology; D001693:Biological Transport, Active; D002247:Carbon Isotopes; D002854:Chromatography, Paper; D003470:Culture Media; D003486:Cyanides / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D004171:Diploidy; D005001:Ethionine / Q000494:pharmacology; D005796:Genes; D005827:Genetics, Microbial; D006710:Homocysteine / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D026901:Membrane Transport Proteins / Q000378:metabolism; D008715:Methionine / Q000378:metabolism*; D009154:Mutation; D012436:S-Adenosylmethionine / Q000378:metabolism; D012440:Saccharomyces / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism; D013696:Temperature
chemical_list: D001386:Azides; D002247:Carbon Isotopes; D003470:Culture Media; D003486:Cyanides; D026901:Membrane Transport Proteins; D006710:Homocysteine; D012436:S-Adenosylmethionine; D003513:Cycloheximide; D008715:Methionine; D000241:Adenosine; D005001:Ethionine