A putative lipopeptide biosynthetic gene cluster is conserved in many species of Actinobacteria, including Mycobacterium tuberculosis and M. marinum, but the specific function of the encoding proteins has been elusive. Using both in vivo heterologous reconstitution and in vitro biochemical analyses, we have revealed that the five encoding biosynthetic enzymes are capable of synthesizing a family of isonitrile lipopeptides (INLPs) through a thio-template mechanism. The biosynthesis features the generation of isonitrile from a single precursor Gly promoted by a thioesterase and a nonheme iron(II)-dependent oxidase homolog and the acylation of both amino groups of Lys by the same isonitrile acyl chain facilitated by a single condensation domain of a nonribosomal peptide synthetase. In addition, the deletion of INLP biosynthetic genes in M. marinum has decreased the intracellular metal concentration, suggesting the role of this biosynthetic gene cluster in metal transport.biosynthetic enzymes | mycobacteria | metal transport S mall-molecule secondary metabolites are produced by microbes as chemical weapons to combat competing organisms or as communication signals to control complex processes such as virulence, morphological differentiation, biofilm formation, and metal acquisition (1-3). One of the most important classes of secondary metabolites are nonribosomal peptides, which are typically biosynthesized by modular nonribosomal peptide synthetases (NRPSs) in an assembly-line manner (4). Two NRPS-encoding gene clusters (mbt and Rv0096-0101) have been identified from the genome of Mycobacterium tuberculosis, the leading causative agent of tuberculosis that currently infects one-third of the world's population. Although the cluster of mbt has been characterized to biosynthesize mycobactin siderophores that form mycobactin-Fe(III) complexes for iron sequestration (5), the role of Rv0096-0101 remains obscure despite various biological studies that have indicated the production of a virulence factor by this gene cluster (6-14). For example, using transposon-site hybridization, Rv0098 to Rv0101 were predicted to be required for M. tuberculosis survival in a mouse model of infection (10). Consistently, a transposon insertion of Rv0097 attenuated M. tuberculosis growth and survival in mice (7).An in silico homology search has revealed that gene clusters homologous to Rv0096-0101 are conserved in pathogenic mycobacteria, such as M. bovis, M. leprae, M. marinum, M. ulcerans, and M. abscessus (Fig. 1), but absent in nonpathogenic mycobacteria such as M. smegmatis, providing further indication of the virulenceassociated nature of the locus product in mycobacteria. Interestingly, in addition to the genus of Mycobacterium, related operons are found in the phylum of Actinobacteria across genera including Streptomyces, Kutzneria, Nocardia, and Rhodococcus (Fig. 1), suggesting a widespread presence of this cluster. Further bioinformatic analysis has shown that five genes (Rv0097-0101) are conserved across all identified gene cluste...
The electron-rich isonitrile is an important functionality in bioactive natural products, but its biosynthesis has been restricted to the IsnA family of isonitrile synthases. We here provide the first structural and biochemical evidence of an alternative mechanism for isonitrile formation. ScoE, a putative non-heme iron(II)-dependent enzyme from Streptomyces coeruleorubidus, was shown to catalyze the conversion of (R)-3-((carboxymethyl)amino)butanoic acid to (R)-3-isocyanobutanoic acid through an oxidative decarboxylation mechanism. This work further provides a revised scheme for the biosynthesis of a unique class of isonitrile lipopeptides, of which several members are critical for the virulence of pathogenic mycobacteria.
A mild and direct strategy for the construction of aryl aminooxetanes has been accomplished through the synergistic combination of photoredox and nickel catalysis. This approach represents a rare example of harnessing challenging tertiary radicals in photoredox/nickel cross-coupling. Oxetanes are often employed in medicinal chemistry as carbonyl or gemdimethyl bioisosteres, but their accessibility is hampered by the lack of practical synthetic methods. The strategy reported here utilizes a readily available oxetanyl amino acid building block in a cross-coupling manifold to rapidly access oxetane scaffolds with broad functional group tolerance. Computational studies reveal that a catalytic cycle beginning with Ni(0)−Ni(II) oxidative addition, rather than radical addition to Ni(0), is operative for reactions with aminooxetanyl radicals. Consequently, for radical-based photoredox/nickel-catalyzed cross-couplings, the preferred mechanistic pathway has a fundamental dependence on the identity of the radical.
The electron-rich isonitrile is an important functionality in bioactive natural products,but its biosynthesis has been restricted to the IsnA family of isonitrile synthases.W eh erein providet he first structural and biochemical evidence of an alternative mechanism for isonitrile formation. ScoE, aputative non-heme iron(II)-dependent enzyme from Streptomyces coeruleorubidus,w as shown to catalyze the conversion of (R)-3-((carboxymethyl)amino)butanoic acid to (R)-3-isocyanobutanoic acid through an oxidative decarboxylation mechanism. This work further provides ar evised scheme for the biosynthesis of au nique class of isonitrile lipopeptides,o f which several members are critical for the virulence of pathogenic mycobacteria.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.
Due to the increased prevalence of obesity in the last decades, bariatric surgery has been on the rise in recent years. Bariatric surgery is a compelling option for weight loss in obese patients with severe obesity-related comorbidities or for whom lifestyle modifications have proven ineffective. Redundant skin following significant weight loss is a common occurrence affecting up to 96% of patients who undergo bariatric surgery, negatively impacting physical and psychosocial health and detracting from activities of daily living. Statistics of the American Society of Plastic Surgeons show that 46,577 body contouring procedures were performed after massive weight loss in the USA in a 2020 report. Abdominoplasty, a well-established cosmetic surgery procedure for improving body contour, is performed by removing excess skin and fat from the abdominal wall and thereby restoring musculofascial integrity and skin elasticity, resulting in a more ideal body shape and increasing quality of life. Although abdominoplasty is a safe procedure, it has been associated with a higher complication rate compared with other body-contouring procedures. Technologic advances over the past decade have been developed as non-invasive alternatives or adjunctive tools to surgery to enhance cosmetic results and minimize complications. New energy-based technologies may supplant invasive surgery for mild to moderate skin laxity and/or diminish the extent of surgery and resulting scars. Plastic surgeons play a significant role in improving the quality of life of patients who suffer from obesity and underwent bariatric surgery. We are deeply convinced, however, that the advancement of knowledge and research in this field will determine the introduction of new technologies and custom-made techniques. This advancement will reduce the complication rate with a rapid reintegration of the patient into the world of work and resumption of daily activities.
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