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Asymmetry in activator ring opens up Sigma54 dependent transcription in bacteria
Author(s) -
CHOWDHURY SAIKAT,
De Carlo Sacha,
Diaz-Avalos Ruben,
Rice William,
Nixon B Tracy
Publication year - 2012
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.26.1_supplement.737.1
Subject(s) - bacterial transcription , transcription (linguistics) , biophysics , dna , rna polymerase , nucleotide , chemistry , activator (genetics) , transcription factor , atp hydrolysis , microbiology and biotechnology , stereochemistry , biology , biochemistry , atpase , rna , enzyme , gene , linguistics , philosophy
Bacterial transcription requires the recruitment of the core RNA‐polymerase (RNAP) to specific promoter by a σ factor. This usually leads to rapid isomerization from un‐melted DNA (closed) to a melted state (open), from which transcription can begin. Unlike this, σ 54 cannot spontaneously isomerize from closed to open complex state. This requires the system to be remodeled by bacterial Enhancer Binding Proteins (bEBPs). They belong to AAA+ ATPases superfamily. These activators are known to act as rings, but how this architecture assists them to perform mechanical work on targets is unknown. Conformational changes occur in the ring during nucleotide binding and hydrolysis. Recent crystal structures have shown heterogeneous nucleotide occupancy in the ring and co‐operative extension of the surface loops, which are believed to contact and remodel the polymerase. Here we present variations in the bEBP structure in the context of closed complex, by transmission electron microscopy. They have shown persistence of ring asymmetry, in the form of a split ring and hints at two possible sequential hydrolysis mechanisms in which the gap propagates around the ring in a constant or varied position relative to the rest of the asymmetric complex. Thus, it helps us to advances our understanding of how bEBPs use ATP binding and hydrolysis to regulate gene expression in bacteria. This work has been supported by NIH.