Padmanabhan Iyer, Subramanian

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Padmanabhan Iyer, Subramanian

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Genética y Microbiología

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Open Access
Coenzyme B12-dependent and independent photoregulation of carotenogenesis across Myxococcales
(Wiley, 2022-01-09) Pérez-Castaño, Ricardo; Bastida-Martínez, Eva; Fernández-Zapata, Jesús; Polanco, María C.; Galbis-Martínez, María L.; Iniesta, Antonio A.; Fontes, Marta; Elías-Arnanz, Montserrat; Padmanabhan Iyer, Subramanian; Genética y Microbiología
Light-induced carotenogenesis in Myxococcus xan- thus is controlled by the B12-based CarH repressor and photoreceptor, and by a separate intricate path- way involving singlet oxygen, the B12-independent CarH paralogue CarA and various other proteins, some eukaryotic-like. Whether other myxobacteria conserve these pathways and undergo photoregulated carotenogenesis is unknown. Here, comparative ana- lyses across 27 Myxococcales genomes identified carotenogenic genes, albeit arranged differently, with carH often in their genomic vicinity, in all three Myxococcales suborders. However, CarA and its associated factors were found exclusively in suborder Cystobacterineae, with carA-carH invariably in tandem in a syntenic carotenogenic operon, except for Cystobacter/Melittangium, which lack CarA but retain all other factors. We experimentally show B12- mediated photoregulated carotenogenesis in repre- sentative myxobacteria, and a remarkably plastic CarH operator design and DNA binding across Myxococcales. Unlike the two characterized CarH from other phyla, which are tetrameric, Cystobacter CarH (the first myxobacterial homologue amenable to analy- sis in vitro) is a dimer that combines direct CarH-like B12-based photoregulation with CarA-like DNA binding and inhibition by an antirepressor. This study pro- vides new molecular insights into B12-dependent pho- toreceptors. It further establishes the B12-dependent pathway for photoregulated carotenogenesis as broadly prevalent across myxobacteria and its evolu- tion, exclusively in one suborder, into a parallel com- plex B12-independent circuit.
Open Access
A ribonuclease III involved in virulence of Mucorales fungi has evolved to cut exclusively single-stranded RNA
(2021) Falk, Sebastian; Zapata Pérez, Rubén; Sánchez Ferrer, Álvaro; Nicolás Molina, Francisco Esteban; Sánchez Ferrer, Álvaro; Navarro Ros, Eusebio; Garre Mula, Victoriano; Padmanabhan Iyer, Subramanian; Cánovas Márquez, José Tomás; Genética y Microbiología
Open Access
A bacterial light response reveals an orphan desaturase for human plasmalogen synthesis
Gallego García, Aránzazu; Monera-Girona, Antonio; Pajares-Martínez, Elena; Bastida-Martínez, Eva; Pérez-Castaño, Ricardo; Iniesta Martínez, Antonio Ángel; Fontes Bastos, Marta; Elías Arnanz, Montserrat; Padmanabhan Iyer, Subramanian; Genética y Microbiología
Plasmalogens are glycerophospholipids with a hallmark sn-1 vinyl ether bond. These lipids are found in animals and some bacteria and have proposed membrane organization, signaling, and antioxidant roles. We discovered the plasmanylethanolamine desaturase activity essential for vinyl ether bond formation in a bacterial enzyme, CarF, which is a homolog of the human enzyme TMEM189. CarF mediates light-induced carotenogenesis in Myxococcus xanthus, and we found that plasmalogens participate in sensing photooxidative stress through singlet oxygen. TMEM189 and other animal homologs could functionally replace CarF in M. xanthus, and knocking out of TMEM189 in a human cell line eliminated plasmalogens. Discovery of the human plasmanylethanolamine desaturase will spur further study of plasmalogen biogenesis, functions, and roles in disease.
Open Access
NMR structure note: N-terminal domain of Thermus thermophilus CdnL
(2012) Gallego García, Aránzazu; Mirassou, Yasmina; Elías Arnanz, Montserrat; Jiménez, Maria Angeles; Padmanabhan Iyer, Subramanian; Genética y Microbiología
Open Access
B12-based photoreceptors: from structure and function to applications in optogenetics and synthetic biology
(2019-08) Pérez-Castaño, Ricardo; Elías Arnanz, Montserrat; Padmanabhan Iyer, Subramanian; Genética y Microbiología
Vitamin B12-based photoreceptor proteins sense ultraviolet (UV), blue or green light using 5´-deoxyadenosylcobalamin (AdoCbl). The prototype of this widespread bacterial photoreceptor family, CarH, controls light-dependent gene expression in photoprotective cellular responses. It represses transcription in the dark by binding to operator DNA as an AdoCbl-bound tetramer, whose disruption by light relieves operator binding to allow transcription. Structures of the "dark" (free and DNA-bound) and "light" CarH states and studies on the unusual AdoCbl photochemistry have provided fundamental insights into these photoreceptors. We highlight these, the plasticity within a conserved mode of action among CarH homologs, their distribution, and their promising applications in optogenetics and synthetic biology.