title: Methionine transport in Pseudomonas aeruginosa.
abstract: A high-affinity (Km = 2.7 x 10(-7) M) energy-requiring methionine-transport system has been characterized in RM 46 and RM 48, two different PAO methionine auxotrophs of Pseudomonas aeruginosa. After 8 s of transport 40--60% of the methionine label in the alcohol extract appears in S-adenosyl-L-methionine (SAM) with the remaining activity in free methionine. Methionine transport required a high degree of structural specificity for transport. Stimulation of transport occurred by addition of glucose or organic acids. The ability of a given substrate to stimulate transport was related to the type of carbon source used for growth. Transport was sensitive to sulfhydryl reagents and required oxidative phosphorylation, as indicated by the inhibitory effects of anaerobiosis, cyanide, and arsenate. The degree of inhibition by arsenate correlated with the level of ATP in the cell. Rapid transport in a SAM-deficient mutant (TM 1) and inhibition by arsenate of transport in this mutant suggested that SAM formation was not directly linked to transport and that ATP supplied energy for transport. Inhibition by arsenate was more severe in glucose- compared to citrate-stimulated cells. This result was also observed with proline transport indicating that this was not a peculiarity of the methionine-transport system. These data emphasize the close link between glucose metabolism, ATP levels, and transport. This ATP level is not so critical for transport in cells metabolizing citrate.
mesh_terms: D000255:Adenosine Triphosphate / Q000096:biosynthesis; D001149:Arsenates / Q000494:pharmacology; D001693:Biological Transport, Active / Q000187:drug effects; D002951:Citrates / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D008715:Methionine / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000378:metabolism*; D012436:S-Adenosylmethionine / Q000096:biosynthesis; D013045:Species Specificity; D013237:Stereoisomerism; D013696:Temperature
chemical_list: D001149:Arsenates; D002951:Citrates; D012436:S-Adenosylmethionine; D000255:Adenosine Triphosphate; D008715:Methionine; D005947:Glucose