Most mycolic acid-containing actinobacteria and some proteobacteria use steroids as growth substrates, but the catabolism of the last two steroid rings has yet to be elucidated. In Mycobacterium tuberculosis, this pathway includes virulence determinants and has been proposed to be encoded by the KstR2-regulated genes, which include a predicted coenzyme A (CoA) transferase gene (ipdAB) and an acyl-CoA reductase gene (ipdC). In the presence of cholesterol, ΔipdC and ΔipdAB mutants of either M. tuberculosis or Rhodococcus jostii strain RHA1 accumulated previously undescribed metabolites: 3aα-H-4α(carboxyl-CoA)-5-hydroxy-7aβ-methylhexahydro-1-indanone (5-OH HIC-CoA) and (R)-2-(2-carboxyethyl)-3-methyl-6-oxocyclohex-1-ene-1-carboxyl-CoA (COCHEA-CoA), respectively. A ΔfadE32 mutant of Mycobacterium smegmatis accumulated 4-methyl-5-oxo-octanedioic acid (MOODA). Incubation of synthetic 5-OH HIC-CoA with purified IpdF, IpdC, and enoyl-CoA hydratase 20 (EchA20), a crotonase superfamily member, yielded COCHEA-CoA and, upon further incubation with IpdAB and a CoA thiolase, yielded MOODA-CoA. Based on these studies, we propose a pathway for the final steps of steroid catabolism in which the 5-member ring is hydrolyzed by EchA20, followed by hydrolysis of the 6-member ring by IpdAB. Metabolites accumulated by ΔipdF and ΔechA20 mutants support the model. The conservation of these genes in known steroid-degrading bacteria suggests that the pathway is shared. This pathway further predicts that cholesterol catabolism yields four propionyl-CoAs, four acetyl-CoAs, one pyruvate, and one succinyl-CoA. Finally, a ΔipdAB M. tuberculosis mutant did not survive in macrophages and displayed severely depleted CoASH levels that correlated with a cholesterol-dependent toxicity. Our results together with the developed tools provide a basis for further elucidating bacterial steroid catabolism and virulence determinants in M. tuberculosis.

Abbreviations: Drp1, dynamin-related protein 1; Drp1 K38A, mutant mouse Drp1 plasmid in which lysine 38 is substituted by alanine; Drp1 WT, wild-type mouse Drp1 plasmid; Drpitor, Drp1 inhibitor; Fis1, mitochondrial fission 1 protein; GMP-PNP, guanosine 5′-[β,γ-imido]triphosphate; HA, hemagglutinin; IC50, half maximal inhibitory concentration; IR, ischemia-reperfusion; mdivi-1, mitochondrial division inhibitor 1; MFC, mitochondrial fragmentation count; MFF, mitochondrial fission factor; MiD49, mitochondrial dynamics protein of 49 kDa; MiD51, mitochondrial dynamics protein of 51 kDa; OMM, outer mitochondrial membrane; ROS, reactive oxygen species; RV, right ventricle; RVEDP, right ventricular end-diastolic pressure; siDrp1, small interfering RNA against Drp1. AbstractMitochondrial fission is important in physiological processes, including coordination of mitochondrial and nuclear division during mitosis, and pathologic processes,

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Unexpected Smiles! An unusual and highly regioselective synthesis of dibenzoxazepinones by a domino sequence assisted by an unexpected Smiles rearrangement is reported. The process is effective on electronically differentiated phenols and shows a high tolerance to variation in the benzamide substituents. A plausible path for the reaction, supported by preliminary mechanistic data, is offered.

Systematic studies are presented demonstrating the complementarity of directed ortho metalation (DoM) and Ir-catalyzed strategies for the provision of borylated aromatics and their subsequent Suzuki-Miyaura coupling reactions. A new concept, the use of the TMS group, readily introduced by DoM, as a latent regiodirective moiety to overcome the otherwise problematic production of isomeric borylated product mixtures is presented. Additional electrophile-induced ipso-deborylation and DoM reactions of the Bpin products are described.