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1.
Structure ; 2024 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-38959899

RESUMO

LoaP is a member of the universal NusG protein family. Previously, we reported that unlike other characterized homologs, LoaP binds RNA sequence-specifically, recognizing a stem-loop in the 5'-untranslated region of operons it regulates. To elucidate how this NusG homolog acquired this ability, we now determined the co-crystal structure of Thermoanaerobacter pseudethanolicus LoaP bound to its cognate 26-nucleotide dfn RNA element. Our structure reveals that the LoaP C-terminal KOW domain recognizes the helical portion of the RNA by docking into a broadened major groove, while a protruding ß-hairpin of the N-terminal NusG-like domain binds the UNCG tetraloop capping the stem-loop. Major-groove RNA recognition is unusual and is made possible by conserved features of the dfn hairpin. Superposition with structures of other NusG proteins implies that LoaP can bind concurrently to the dfn RNA and the transcription elongation complex, suggesting a new level of co-transcriptional regulation by proteins of this conserved family.

2.
J Mol Biol ; 433(15): 167100, 2021 07 23.
Artigo em Inglês | MEDLINE | ID: mdl-34119489

RESUMO

Bacterial NusG associates with RNA polymerase (RNAP) through its N-terminal domain, while the C-terminal domain (CTD) forms dynamic interactions with Rho, S10, NusB and NusA to affect transcription elongation. While virtually all bacteria encode for a core NusG, many also synthesize paralogs that transiently bind RNAP to alter expression of targeted genes. Yet, despite the importance of the genes they regulate, most of the subfamilies of NusG paralogs (e.g., UpxY, TaA, ActX and LoaP) have not been investigated in depth. Herein, we discover that LoaP requires a small RNA hairpin located within the 5' leader region of its targeted operons. LoaP binds the RNA element with nanomolar affinity and high specificity, in contrast to other NusG proteins, which have not been shown to exhibit RNA-binding activity. These data reveal a sequence feature that can be used to identify LoaP-regulated operons. This discovery also expands the repertoire of macromolecular interactions exhibited by the NusG CTD during transcription elongation to include an RNA ligand.


Assuntos
Bacillus/genética , Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , RNA Bacteriano/metabolismo , Proteínas de Ligação a RNA/química , Proteínas de Ligação a RNA/metabolismo , Regiões 5' não Traduzidas , Bacillus/metabolismo , RNA Polimerases Dirigidas por DNA/metabolismo , Conformação Molecular , Óperon , Domínios Proteicos , RNA Bacteriano/química
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