The myxochelin iron transport regulon of the myxobacterium Stigmatella aurantiaca Sg a15.
The biosynthetic gene cluster of the myxochelin-type iron chelator was cloned from Stigmatella aurantiaca Sg a15 and characterized. This catecholate siderophore was only known from two other myxobacteria. The biosynthetic genes of 2,3-dihydroxybenzoic acid are located in the cluster (mxcC-mxcF). Two molecules of 2, 3-dihydroxybenzoic acid are activated and condensed with lysine in a unique way by a protein homologous to nonribosomal peptide synthetases (MxcG). Inactivation of mxcG, which encodes an adenylation domain for lysine, results in a myxochelin negative mutant unable to grow under iron-limiting conditions. Growth could be restored by adding Fe3+, myxochelin A or B to the medium. Inactivation of mxcD leads to the same phenotype. A new type of reductive release from nonribosomal peptide synthetases of the 2, 3-dihydroxybenzoic acid bis-amide of lysine from MxcG, catalyzed by a protein domain with homology to NAD(P) binding sites, is discussed. The product of a gene, encoding a protein similar to glutamate-1-semialdehyde 2,1-aminomutases (mxcL), is assumed to transaminate the aldehyde that is proposed as an intermediate. Further genes encoding proteins homologous to typical iron utilization and iron uptake polypeptides are reported.
Silakowski
B
B
GBF-Gesellschaft für Biotechnologische Forschung mbH, Braunschweig, Germany.
Kunze
B
B
Nordsiek
G
G
Blöcker
H
H
Höfle
G
G
Müller
R
R
D000595:Amino Acid Sequence; D001692:Biological Transport; D002851:Chromatography, High Pressure Liquid; D017124:Conserved Sequence; D015964:Gene Expression Regulation, Bacterial; D062385:Hydroxybenzoates / Q000378:metabolism; D019751:Intramolecular Transferases / Q000235:genetics / Q000378:metabolism; D007501:Iron / Q000378:metabolism*; D007502:Iron Chelating Agents / Q000378:metabolism; D008239:Lysine / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics; D009154:Mutation / Q000235:genetics; D009876:Operon / Q000235:genetics; D017434:Protein Structure, Tertiary; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D018085:Regulon / Q000235:genetics*; D016415:Sequence Alignment; D020606:Stigmatella aurantiaca / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*
D062385:Hydroxybenzoates; D007502:Iron Chelating Agents; C058735:myxochelin A; C009135:2,3-dihydroxybenzoic acid; D007501:Iron; D019751:Intramolecular Transferases; C058486:isochorismate synthase; D008239:Lysine