biostudies-literatureBrezovska BCzech Academy of SciencesMEYS, Funded by the European Union-Next Generation EUCzech Science Foundatione0006624https://www.ebi.ac.uk/biostudies/studies/S-EPMC11656743biostudies-literatureUnknown206(12)In mycobacteria, σ^A is the primary sigma factor. This essential protein binds to RNA polymerase (RNAP) and mediates transcription initiation of housekeeping genes. Our knowledge about this factor in mycobacteria is limited. Here, we performed an unbiased search for interacting partners of <i>Mycobacterium smegmatis</i> σ^A. The search revealed a number of proteins; prominent among them was MoaB2. The σ^A-MoaB2 interaction was validated and characterized by several approaches, revealing that it likely does not require RNAP and is specific, as alternative σ factors (<i>e.g.</i>, closely related σ^B) do not interact with MoaB2. The structure of MoaB2 was solved by X-ray crystallography. By immunoprecipitation and nuclear magnetic resonance, the unique,Journal of bacteriologyMoaB2, a newly identified transcription factor, binds to σ^A in <i>Mycobacterium smegmatis</i>.PMC1165674323-05622S19-12956S22-12023SLX22NPO5103RVO: 86652036Hubalek MBorah NHnilicova JPospisilova DZidek LSikova MKrenkova AShoman MJanouskova MKambova MBrezovska BDohnalek JNarasimhan SKoval TKomarek JSanderova HTuzincin DHalada PTrundova MKrasny LVankova Hausnerova VCerny MfalseMoaB2, a newly identified transcription factor, binds to σ^A in <i>Mycobacterium smegmatis</i>.In mycobacteria, σ^A is the primary sigma factor. This essential protein binds to RNA polymerase (RNAP) and mediates transcription initiation of housekeeping genes. Our knowledge about this factor in mycobacteria is limited. Here, we performed an unbiased search for interacting partners of <i>Mycobacterium smegmatis</i> σ^A. The search revealed a number of proteins; prominent among them was MoaB2. The σ^A-MoaB2 interaction was validated and characterized by several approaches, revealing that it likely does not require RNAP and is specific, as alternative σ factors (<i>e.g.</i>, closely related σ^B) do not interact with MoaB2. The structure of MoaB2 was solved by X-ray crystallography. By immunoprecipitation and nuclear magnetic resonance, the unique,2024-01-01T00:00:00Z2024 Dec2026-06-01T19:48:37.948Z2025-04-04T00:38:42.659ZS-EPMC116567433949908810.1128/jb.00066-24