PMID:12511507

Citation	Okamoto, S, Lezhava, A, Hosaka, T, Okamoto-Hosoya, Y and Ochi, K (2003) Enhanced expression of S-adenosylmethionine synthetase causes overproduction of actinorhodin in Streptomyces coelicolor A3(2). J. Bacteriol. 185:601-9
Abstract	We found that a 46-kDa protein is highly expressed in an actinorhodin-overproducing Streptomyces coelicolor A3(2) mutant (KO-179), which exhibited a low-level resistance to streptomycin. The protein was identified as S-adenosylmethionine (SAM) synthetase, which is a product of the metK gene. Enzyme assay revealed that SAM synthetase activity in strain KO-179 was 5- to 10-fold higher than in wild-type cells. The elevation of SAM synthetase activity was found to be associated with an increase in the level of intracellular SAM. RNase protection assay revealed that the metK gene was transcribed from two distinct promoters (p1 and p2) and that enhanced expression of the MetK protein in the mutant strain KO-179 was attributed to elevated transcription from metKp2. Strikingly, the introduction of a high-copy-number plasmid containing the metK gene into wild-type cells resulted in a precocious hyperproduction of actinorhodin. Furthermore, the addition of SAM to the culture medium induced Act biosynthesis in wild-type cells. Overexpression of metK stimulated the expression of the pathway-specific regulatory gene actII-ORF4, as demonstrated by the RNase protection assay. The addition of SAM also caused hyperproduction of streptomycin in Streptomyces griseus. These findings implicate the significant involvement of intracellular SAM in initiating the onset of secondary metabolism in STREPTOMYCES:
Links	PubMed PMC145329
Keywords	Amino Acid Sequence; Anthraquinones/metabolism; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Base Sequence; Electrophoresis, Gel, Two-Dimensional; Gene Expression Regulation, Bacterial; Methionine Adenosyltransferase/genetics; Methionine Adenosyltransferase/metabolism; Molecular Sequence Data; S-Adenosylmethionine/metabolism; Sequence Analysis, DNA; Streptomyces/enzymology; Streptomyces/genetics; Streptomyces/metabolism; Transcription, Genetic
edit table

Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
STRCO:METK		GO:0006556: S-adenosylmethionine biosynthetic process	ECO:0000315:		P		Table 1: as expected, the level of intracellular SAM in KO-179 was found to be markedly elevated relative to the wild-type strain.	complete CACAO 2572

References

See Help:References for how to manage references in GONUTS.