Nucleotide-induced asymmetry within ATPase activator ring drives σ54-RNAP interaction and ATP hydrolysis.
It is largely unknown how the typical homomeric ring geometry of ATPases associated with various cellular activities enables them to perform mechanical work. Small-angle solution X-ray scattering, crystallography, and electron microscopy (EM) reconstructions revealed that partial ATP occupancy caused the heptameric closed ring of the bacterial enhancer-binding protein (bEBP) NtrC1 to rearrange into a hexameric split ring of striking asymmetry. The highly conserved and functionally crucial GAFTGA loops responsible for interacting with σ54-RNA polymerase formed a spiral staircase. We propose that splitting of the ensemble directs ATP hydrolysis within the oligomer, and the ring's asymmetry guides interaction between ATPase and the complex of σ54 and promoter DNA. Similarity between the structure of the transcriptional activator NtrC1 and those of distantly related helicases Rho and E1 reveals a general mechanism in homomeric ATPases whereby complex allostery within the ring geometry forms asymmetric functional states that allow these biological motors to exert directional forces on their target macromolecules.
Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA;
Tatyana A
TA
Sysoeva
Saikat
S
Chowdhury
Liang
L
Guo
B Tracy
BT
Nixon
D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D006868:Hydrolysis; D007711:Klebsiella pneumoniae / Q000235:genetics; D008958:Models, Molecular; D009711:Nucleotides / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051877:RNA Polymerase Sigma 54 / Q000378:metabolism*; D016962:Sinorhizobium meliloti / Q000235:genetics
D004268:DNA-Binding Proteins; D009711:Nucleotides; D000255:Adenosine Triphosphate; D012321:DNA-Directed RNA Polymerases; D051877:RNA Polymerase Sigma 54; D000251:Adenosine Triphosphatases
AAA+ ATPase; bacterial enhancer-binding protein (bEBP); mechanochemical ATPases; multimeric ATPases; σ54-dependent transcription; σ54-dependent transcription activators