Molecular characterization of co-transcribed genes from

Abstract

Six genes (nikA, nikB, nikD, nikE, nikF, and nikG) from Streptomyces tendae Tü901 were identified by sequencing the region surrounding the nikC gene, which encodes L-lysine 2-aminotransferase, previously shown to catalyze the initial reaction in the biosynthesis of hydroxypyridylhomothreonine, the peptidyl moiety of the peptidyl nucleoside antibiotic nikkomycin. These genes, together with the nikC gene, span a DNA region of 7.87 kb and are transcribed as a polycistronic mRNA in a growth-phase dependent manner. The sequences of the deduced proteins NikA and NikB exhibit significant similarity to those of acetaldehyde dehydrogenases and 4-hydroxy-2-oxovalerate aldolases, respectively, which are involved in meta-cleavage degradation of aromatic hydrocarbons. The predicted NikD gene product shows sequence similarity to monomeric sarcosine oxidases, and the deduced NikE protein belongs to the superfamily of adenylate-forming enzymes. The nikF gene and the nikG gene encode a cytochrome P450 monooxygenase and a ferredoxin, respectively. Disruption of any of the genes nikA, nikB, nikD, nikE and nikF by insertion of a kanamycin resistance cassette abolished formation of the biologically active nikkomycins I, J, X, and Z. The nikA, nikB, nikD, and nikE mutants accumulated the nucleoside moieties nikkomycins Cx and Cz. In the nikD and nikE mutants nikkomycin production (nikkomycins I, J, X, Z) could be restored by feeding with picolinic acid and hydroxypyridylhomothreonine, respectively. The nikF mutant exclusively produced novel derivatives, nikkomycins Lx and Lz, which contain pyridylhomothreonine as the peptidyl moiety. Our results indicate that the nikA, nikB, nikD, nikE, nikF, and nikG genes, in addition to nikC, function in the biosynthetic pathway leading to hydroxypyridylhomothreonine, the putative activities of each of their products are discussed.

Structural Characterization of OxyD, a Cytochrome P450 Involved in β-Hydroxytyrosine Formation in Vancomycin Biosynthesis

“…Exceptions are: (1) Small residue (S, G, A), (2) Positively Charged Residue (K, H, R), (3) Majority Hydrophobic (L, V; also S and G), (4) Majority Small (S, A; also V). b Percentage of residues matching to the overall consensus rule, based upon similarity.…”

iso-Migrastatin, Migrastatin, and Dorrigocin Production in Streptomyces platensis NRRL 18993 Is Governed by a Single Biosynthetic Machinery Featuring an Acyltransferase-less Type I Polyketide Synthase

“…5B). The deduced gene product of mgsI displays high homology to putative oxidoreductases of bacterial origin, that of mgsJ shows high homology to MitM (54% identity), an O-methyltransferase involved in mitomycin biosynthesis from Streptomyces lavendulae NRRL 2564 (46), and MgsK resembles the NikF P-450 hydroxylase (48% identity) involved in nikkomycin biosynthesis (47).…”

NewL-Amino Acid Ligases Catalyzing Oligopeptide Synthesis from Various Microorganisms

“…For these candidates, only the role of NikS was predicted, and it was reported to be essential for the biosynthesis of a nikkomycin antibiotic. [22][23][24] The enzyme activity of NikS has not yet been clarified, but it may be involved in the ligation process. In addition, SanS, whose amino acid sequence shows 98% identity with that of NikS, has been reported to hydrolyze ATP to ADP and phosphate, but its peptide synthesis activity has not been reported.…”