Details

Autor(en) / Beteiligte

• Pfennig, F
• Schauwecker, F
• Keller, U

Titel

Molecular Characterization of the Genes of Actinomycin Synthetase I and of a 4-Methyl-3-hydroxyanthranilic Acid Carrier Protein Involved in the Assembly of the Acylpeptide Chain of Actinomycin in Streptomyces

Ist Teil von

• The Journal of biological chemistry, 1999-04, Vol.274 (18), p.12508-12516

Ort / Verlag

United States: American Society for Biochemistry and Molecular Biology

Erscheinungsjahr

1999

Link zum Volltext

Quelle

Free E-Journal (出版社公開部分のみ）

Beschreibungen/Notizen

• Actinomycin synthetase I (ACMS I) activates 4-methyl-3-hydroxyanthranilic acid, the precursor of the chromophoric moiety of the actinomycin, as adenylate. The gene acmA of ACMS I was identified upstream of the genes acmB and acmC encoding the two peptide synthetases ACMS II and ACMS III, respectively, which assemble the pentapeptide lactone rings of the antibiotic. Sequence analysis and expression of acmA in Streptomyces lividans as enzymatically active hexa-His-fusion confirmed the acmA gene product to be ACMS I. An open reading frame of 234 base pairs ( acmD ), which encodes a 78-amino acid protein with similarity to various acyl carrier proteins, is located downstream of acmA . The acmD gene was expressed in Escherichia coli as hexa-His-fusion protein (Acm acyl carrier protein (AcmACP)). ACMS I in the presence of ATP acylated the purified AcmACP with radioactive p -toluic acid, used as substrate in place of 4-MHA. Only 10% of the AcmACP from E. coli was acylated, suggesting insufficient modification with 4′-phosphopantetheine cofactor. Incubation of this AcmACP with a holo-ACP synthase and coenzyme A quantitatively established the holo-form of AcmACP. Enzyme assays in the presence of ACMS II showed that toluyl-AcmACP directly acylated the thioester-bound threonine on ACMS II. Thus, AcmACP is a 4-MHA carrier protein in the peptide chain initiation of actinomycin synthesis.