Stigmatella aurantiaca

A myxobacterium Stigmatella aurantiaca uses stigmolone (22) as its fruiting body inducing pheromone. Both the enantiomers of 22 were synthesized by Mori [56] and also byEnders [57], and found to be equally bioactive. Scheme 33 shows Mori s synthesis, and Scheme 34 summarizes that of Enders. Since both (R)- and (S)-22 were bioactive, ( )-22 was synthesized in a very efficient manner by Kulinkovich (Scheme 35) [58]. 

Progress has also been reported in applying titanium-mediated cydopropanation reactions as a key step in the preparation of natural products. For example, racemic stigmo-lone (8-hydroxy-2,5,8-trimethylnonan-4-one) 163, a pheromone of the myxobacterium Stigmatella aurantiaca, has been synthesized in 67% overall yield by the titanium-mediated hydroxycyclopropanation of 2-methyl-5-hexen-2-ol 161 with ethyl isovalerate 160 followed by base-induced ring-opening of the resulting 2-(3-hydroxy-3-methylbutyl)-1-isobutyl-l-cyclopropanol 162 (Scheme 11.41) [139]. 

More recently two functionally redundant Sfp-type PPTase, MxPptl and MxPptZ, have been found to differentially activate biosynthetic pathways in Myxococcus xanthus MxPptl and MxPptZ exhibit broad substrate specificity as supported by the fact that the complex PKS-NRPS hydrids epothilone and myxothiazol from Sorangium cellulosum and Stigmatella aurantiaca, respectively, could be expressed in M. xanthus without the need for an external PPTase. 

Q092U4 Stigmatella aurantiaca DW4/3-1 (6-amlnohexanoate-cyclic-dimer hydrolase) (0.2373)... 

Stigmatella aurantiaca Pseudomonas entomophiia Pseudomonas putida... 

Arabidopsis thaliana Oryza sativa Thai ictrum flavuiti Papaver somniferuiti Aris toloch i a contorta Petroselinum crispum Rhodiola sachalinensis Stigmatella aurantiaca Pseudomonas entomophila Pseudomonas putida Aspergillus clavatus Neosartorya fischeri Drosophila melanogaster Apis mellifera Conserved sites Conserved sites (plants)... 

Bode H. B., Zeggel B., Silakowski B., Wenzel S. C., Hans R., and Muller R. (2003) Steroid biosynthesis in prokaryotes identification of myxobacterial steroids and cloning of the first bacterial 2,3(S)-oxidosqualene cyclase from the myx-obacterium Stigmatella aurantiaca. Mol. Microbiol. 47, 471-481. 

In the bacteria Stigmatella aurantiaca, y-carotene (27) occurs with 4-keto-, T,2 -dihydro-r-hydroxy-, and 4-keto-r,2 -dihydro-T-hydroxy-y-carotene. In addition, the dehydrogenation product 4-keto-l, 2 -dihydro-r-hydroxy-torulene (cf. 28) was present. Two intermediates (29) and (30) between torulene (28) and torularhodin (31) have been isolated from a yeast. ... 

Figure 7 Type I PKS biosynthesis in myxobacteria (b). Biosynthesis of stigmatellin A (14) in Stigmatella aurantiaca Sg a15. The KR domain from module 8 (marked with an asterisk) is most likely inactive. The hydroxy group generated by module 2 by reduction of the first extender unit is assumed to be dehydrated by the module 7 DH domain. StiH and StiJ incorporate three malonyl-CoA extender units in total. Thus, one of these modules appears to function iteratively. The polyketide chain is released and cyclized by the terminal Cyc domain, most likely via intermediate 22, and further decorated in post-PKS biosynthetic steps catalyzed by StiK and StiL. The stereochemistry of the linear intermediates bound to the enzyme complex was assigned based on the absolute configuration of 14.

Figure 8 Type II PKS biosynthesis In myxobacteria. Biosynthesis of aurachin D (19) In Stigmatella aurantiaca Sg a15. The biosynthetic steps that are catalyzed by the gene products (AuaA-AuaE) from the aurachin core cluster are shown (AuaA, prenyl transferase AuaB, ACP AuaC, KSa AuaD, KS/3 and AuaE, benzoate CoA ligase). Binding of anthranlloyl-CoA to the ACP domain has not been proven experimentally, so direct binding of the starter unit to the KSa might be possible.

Figure 11 Nonribosomal peptide biosynthesis in myxobacteria (b). Biosynthesis of myxochelin A (13) and myxochelin B (32) in Stigmatella aurantiaca Sg at 5. The biosynthetic compiex represents a nonlinear NRPS system composed of a split loading moduie (MxcE and MxcF) and an eiongation moduie (MxcG), which catalyzes two condensation steps. The terminal Red domain was recentiy shown to reiease the aidehyde 31, which can undergo a further round of Red-catalyzed reduction to yieid 13 or be reductiveiy transaminated by MxcL to produce 32.

Myxochromide S Stigmatella aurantiaca Pseudomonas putida 40mgl 116... 

Silakowski, B., Nordsiek, G., Kunze, B., Blocker, H., and MUller, R. (2001). Novel features in a combined polyketide synthase/non-ribosomal peptide synthetase The myxalamid biosynthetic gene cluster of the myxobacterium Stigmatella aurantiaca Sgal5. Chem. Biol. 8, 59-69. 

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