Biosynthetic tailoring of microcin E492m: post-translational modification affords an antibacterial siderophore-peptide conjugate.
The present work reveals that four proteins, MceCDIJ, encoded by the MccE492 gene cluster are responsible for the remarkable post-translational tailoring of microcin E492 (MccE492), an 84-residue protein toxin secreted by Klebsiella pneumonaie RYC492 that targets neighboring Gram-negative species. This modification results in attachment of a linearized and monoglycosylated derivative of enterobactin, a nonribosomal peptide and iron scavenger (siderophore), to the MccE492m C-terminus. MceC and MceD derivatize enterobactin by C-glycosylation at the C5 position of a N-(2,3-dihydroxybenzoyl)serine (DHB-Ser) moiety and regiospecific hydrolysis of an ester linkage in the trilactone scaffold, respectively. MceI and MceJ form a protein complex that attaches C-glycosylated enterobactins to the C-terminal serine residue of both a C10 model peptide and full-length MccE492. In the enzymatic product, the C-terminal serine residue is covalently attached to the C4' oxygen of the glucose moiety. Nonenzymatic and base-catalyzed migration of the peptide to the C6' position affords the C6' glycosyl ester linkage observed in the mature toxin, MccE492m, isolated from bacterial cultures.
Nolan
Elizabeth M
EM
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA.
Fischbach
Michael A
MA
Koglin
Alexander
A
Walsh
Christopher T
CT
D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000096:biosynthesis* / Q000633:toxicity; D001430:Bacteriocins / Q000096:biosynthesis* / Q000633:toxicity; D001692:Biological Transport; D005947:Glucose / Q000737:chemistry / Q000378:metabolism; D006031:Glycosylation; D006868:Hydrolysis; D007709:Klebsiella / Q000737:chemistry / Q000378:metabolism; D008956:Models, Chemical; D008969:Molecular Sequence Data; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D012694:Serine / Q000737:chemistry / Q000378:metabolism; D017262:Siderophores / Q000737:chemistry / Q000378:metabolism*; D013997:Time Factors
D000900:Anti-Bacterial Agents; D001430:Bacteriocins; D010455:Peptides; D017262:Siderophores; C020411:microcin; D012694:Serine; D005947:Glucose; D010100:Oxygen