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Báo cáo Y học: A b-lysine adenylating enzyme and a b-lysine binding protein involved in poly b-lysine chain assembly in nourseothricin synthesis in Streptomyces noursei

Nourseothricins (syn. Streptothricins), agroupof nucleoside peptides produced by several streptomycete strains, contain a polyb-lysine chain of variable length attached in amide linkage to the amino sugar moiety gulosamine of the nucleoside portion. We show that the nourseothricin-pro-ducingStreptomyces nourseicontains an enzyme (NpsA) of an apparentMr56 000 that speci®cally activatesb-lysine by adenylation but does not bind to it as a thioester. | Eur. J. Biochem. 269 347-357 2002 FEBS 2002 A b-lysine adenylating enzyme and a b-lysine binding protein involved in poly b-lysine chain assembly in nourseothricin synthesis in Streptomyces noursei Nicolas Grammel Kvitka Pankevych2 Julia Demydchuk2 Klaus Lambrecht2 Hans-Peter Saluz2 Ullrich Keller1 and Hans Krugel2 1Max-Volmer-Institut fur Biophysikalische Chemie und Biochemie Fachgebiet Biochemie und Molekulare Biologie Technische Universităt Berlin Germany department of Cell and Molecular Biology Hans Knoll Institute for Natural Product Research Jena Germany Nourseothricins syn. Streptothricins a group of nucleoside peptides produced by several streptomycete strains contain a poly b-lysine chain of variable length attached in amide linkage to the amino sugar moiety gulosamine of the nucleoside portion. We show that the nourseothricin-pro-ducing Streptomyces noursei contains an enzyme NpsA of an apparent Mr 56 000 that specifically activates b-lysine by adenylation but does not bind to it as a thioester. Cloning and sequencing of npsA from S. noursei including its flanking DNA regions revealed that it is closely linked to the nourseothricin resistance gene nail and some other genes on the chromosome possibly involved in nourseothricin biosynthesis. The deduced amino-acid sequence revealed that NpsA is a stand-alone adenylation domain with similarity to the adenylation domains of nonribosomal peptide synthetases NRPS . Further analysis revealed that S. noursei contains a b-lysine binding enzyme NpsB of about Mr 64 100 which can be loaded by NpsA with b-lysine as a thioester. Analysis of the deduced amino-acid sequence from the gene npsB of NpsB showed that it consists of two domains. The N-terminal domain of w 100 amino-acid residues has high similarity to PCP domains of NRPSs whereas the 450-amino-acid C-terminal domain has a high similarity to epimerization E -domains of NRPSs. Remarkably in this E-domain the conserved H-H-motif is changed to H-Q which suggests .