title: Mixing Up the Pieces of the Desferrioxamine B Jigsaw Defines the Biosynthetic Sequence Catalyzed by DesD.
abstract: Late-stage assembly of the trimeric linear siderophore desferrioxamine B (DFOB) native to Streptomyces pilosus involves two DesD-catalyzed condensation reactions between one N-acetyl-N-hydroxy-1,5-diaminopentane (AHDP) unit and two N-succinyl-N-hydroxy-1,5-diaminopentane (SHDP) units. AHDP and SHDP are products of DesBC-catalyzed reactions of the native diamine substrate 1,5-diaminopentane (DP). The sequence of DesD-catalyzed DFOB biosynthesis was delineated by analyzing the distribution of DFOB analogues and dimeric precursors assembled by S. pilosus in medium containing 1,4-diamino-2(E)-butene (E-DBE). Seven unsaturated DFOB analogues were produced that were partially resolved by liquid chromatography (LC). Mass spectrometry (MS) measurements reported on the combination of E-DBE- and DP-derived substrates in each trimer (uDFOA1 series, 1:2; uDFOA2 series, 2:1; uDFOA3, 3:0). MS/MS fragmentation patterns reported on the absolute position of the substrate derivative at the N-acetylated terminus, the internal region, or the amine terminus of the trimer. The uDFOA1 and uDFOA2 series each comprised three constitutional isomers (binary notation (DP-derived substrate "0," E-DBE-derived substrate "1"); direction, N-acetylated-internal-amine): uDFOA1[001], uDFOA1[010], uDFOA1[100]; and uDFOA2[011], uDFOA2[110], and uDFOA2[101]. E-DBE completely replaced DP in uDFOA3[111]. Relative concentrations of the uDFOA1 series were uDFOA1[001] ≫ uDFOA1[100] > uDFOA1[010] and of the uDFOA2 series, uDFOA2[101] > uDFOA2[011] ≫ uDFOA2[110]. Dimeric compounds assembled from one N-acetylated and one N-succinylated substrate derivative were detected as trimer precursors: dDFX[00-] ≫ udDFX[10-] > udDFX[01-] (d = dimer, vacant position "-"). Relative concentrations of all species were consistent with the biosynthetic sequence: (i) SHDP activation, (ii) condensation with AHDP to form AHDP-SHDP, (iii) SHDP activation, and (iv) condensation with AHDP-SHDP to form DFOB.
authors.affiliation: School of Medical Sciences (Pharmacology) and Bosch Institute, The University of Sydney , Sydney, New South Wales 2006, Australia.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Telfer
authors.affiliation: School of Medical Sciences (Pharmacology) and Bosch Institute, The University of Sydney , Sydney, New South Wales 2006, Australia.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Gotsbacher
authors.affiliation: School of Medical Sciences (Pharmacology) and Bosch Institute, The University of Sydney , Sydney, New South Wales 2006, Australia.
authors.forename: Cho Zin
authors.initials: CZ
authors.lastname: Soe
authors.affiliation: School of Medical Sciences (Pharmacology) and Bosch Institute, The University of Sydney , Sydney, New South Wales 2006, Australia.
authors.forename: Rachel
authors.initials: R
authors.lastname: Codd
mesh_terms: D053898:Biosynthetic Pathways; D002853:Chromatography, Liquid; D003676:Deferoxamine / Q000737:chemistry / Q000378:metabolism*; D017262:Siderophores / Q000737:chemistry / Q000378:metabolism*; D013302:Streptomyces / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism; D053719:Tandem Mass Spectrometry
chemical_list: D017262:Siderophores; D003676:Deferoxamine