Summary information

PDB id
8eyu
Class
RNA
Method
X-ray (1.95 Å)
Summary
Structure of beetroot dimer bound to dfame
Reference
Passalacqua LFM, Starich MR, Link KA, Wu J, Knutson JR, Tjandra N, Jaffrey SR, Ferre-D'Amare AR (2023): "Co-crystal structures of the fluorogenic aptamer Beetroot show that close homology may not predict similar RNA architecture." Nat Commun, 14, 2969. doi: 10.1038/s41467-023-38683-3.
Abstract
Beetroot is a homodimeric in vitro selected RNA that binds and activates DFAME, a conditional fluorophore derived from GFP. It is 70% sequence-identical to the previously characterized homodimeric aptamer Corn, which binds one molecule of its cognate fluorophore DFHO at its interprotomer interface. We have now determined the Beetroot-DFAME co-crystal structure at 1.95 Å resolution, discovering that this RNA homodimer binds two molecules of the fluorophore, at sites separated by ~30 Å. In addition to this overall architectural difference, the local structures of the non-canonical, complex quadruplex cores of Beetroot and Corn are distinctly different, underscoring how subtle RNA sequence differences can give rise to unexpected structural divergence. Through structure-guided engineering, we generated a variant that has a 12-fold fluorescence activation selectivity switch toward DFHO. Beetroot and this variant form heterodimers and constitute the starting point for engineered tags whose through-space inter-fluorophore interaction could be used to monitor RNA dimerization.
G4 notes
6 G-tetrads, 1 G4 helix, 2 G4 stems, 1 G4 coaxial stack, 2(-P-P-P), parallel(4+0), UUUU, coaxial interfaces: 5'/5'

Base-block schematics in six views

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List of 6 G-tetrads

 1 glyco-bond=ss-- sugar=---- groove=-w-n planarity=0.306 type=bowl   nts=4 GGGG B.G18,B.G35,B.G27,B.G22
 2 glyco-bond=---- sugar=-333 groove=---- planarity=0.252 type=other  nts=4 GGGG B.G20,B.G24,B.G29,B.G32
 3 glyco-bond=---- sugar=33-3 groove=---- planarity=0.128 type=planar nts=4 GGGG B.G21,B.G25,B.G30,B.G33
 4 glyco-bond=sss- sugar=---- groove=--wn planarity=0.352 type=bowl-2 nts=4 GGGG A.G18,A.G35,A.G27,A.G22
 5 glyco-bond=---- sugar=-333 groove=---- planarity=0.281 type=other  nts=4 GGGG A.G20,A.G24,A.G29,A.G32
 6 glyco-bond=---- sugar=33-3 groove=---- planarity=0.152 type=planar nts=4 GGGG A.G21,A.G25,A.G30,A.G33

List of 1 G4-helix

In DSSR, a G4-helix is defined by stacking interactions of G-tetrads, regardless of backbone connectivity, and may contain more than one G4-stem.

Helix#1, 6 G-tetrad layers, inter-molecular, with 2 stems

 1  glyco-bond=ss-- sugar=---- groove=-w-n Major-->WC nts=4 GGGG B.G18,B.G35,B.G27,B.G22
 2  glyco-bond=---- sugar=3-33 groove=---- Major-->WC nts=4 GGGG B.G33,B.G30,B.G25,B.G21
 3* glyco-bond=---- sugar=333- groove=---- Major-->WC nts=4 GGGG B.G32,B.G29,B.G24,B.G20
 4  glyco-bond=---- sugar=3-33 groove=---- WC-->Major nts=4 GGGG A.G32,A.G20,A.G24,A.G29
 5  glyco-bond=---- sugar=333- groove=---- WC-->Major nts=4 GGGG A.G33,A.G21,A.G25,A.G30
 6  glyco-bond=s-ss sugar=---- groove=nw-- WC-->Major nts=4 GGGG A.G18,A.G22,A.G27,A.G35
  step#1  mp(<<,backward) area=7.28  rise=3.51 twist=34.8
  step#2  mp(<<,backward) area=11.59 rise=3.40 twist=29.7
  step#3  mm(<>,outward)  area=8.46  rise=3.20 twist=-57.2
  step#4  pm(>>,forward)  area=11.39 rise=3.43 twist=30.4
  step#5  pm(>>,forward)  area=8.32  rise=3.52 twist=33.1
  strand#1 RNA glyco-bond=s----s sugar=-3333- nts=6 GGGGGG B.G18,B.G33,B.G32,A.G32,A.G33,A.G18
  strand#2 RNA glyco-bond=s----- sugar=--3-3- nts=6 GGGGGG B.G35,B.G30,B.G29,A.G20,A.G21,A.G22
  strand#3 RNA glyco-bond=-----s sugar=-3333- nts=6 GGGGGG B.G27,B.G25,B.G24,A.G24,A.G25,A.G27
  strand#4 RNA glyco-bond=-----s sugar=-3-3-- nts=6 GGGGGG B.G22,B.G21,B.G20,A.G29,A.G30,A.G35

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5 stacking diagrams
 1  glyco-bond=ss-- sugar=---- groove=-w-n Major-->WC nts=4 GGGG B.G18,B.G35,B.G27,B.G22
2 glyco-bond=---- sugar=3-33 groove=---- Major-->WC nts=4 GGGG B.G33,B.G30,B.G25,B.G21
step#1 mp(<<,backward) area=7.28 rise=3.51 twist=34.8

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 2  glyco-bond=---- sugar=3-33 groove=---- Major-->WC nts=4 GGGG B.G33,B.G30,B.G25,B.G21
3* glyco-bond=---- sugar=333- groove=---- Major-->WC nts=4 GGGG B.G32,B.G29,B.G24,B.G20
step#2 mp(<<,backward) area=11.59 rise=3.40 twist=29.7

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 3* glyco-bond=---- sugar=333- groove=---- Major-->WC nts=4 GGGG B.G32,B.G29,B.G24,B.G20
4 glyco-bond=---- sugar=3-33 groove=---- WC-->Major nts=4 GGGG A.G32,A.G20,A.G24,A.G29
step#3 mm(<>,outward) area=8.46 rise=3.20 twist=-57.2

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 4  glyco-bond=---- sugar=3-33 groove=---- WC-->Major nts=4 GGGG A.G32,A.G20,A.G24,A.G29
5 glyco-bond=---- sugar=333- groove=---- WC-->Major nts=4 GGGG A.G33,A.G21,A.G25,A.G30
step#4 pm(>>,forward) area=11.39 rise=3.43 twist=30.4

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 5  glyco-bond=---- sugar=333- groove=---- WC-->Major nts=4 GGGG A.G33,A.G21,A.G25,A.G30
6 glyco-bond=s-ss sugar=---- groove=nw-- WC-->Major nts=4 GGGG A.G18,A.G22,A.G27,A.G35
step#5 pm(>>,forward) area=8.32 rise=3.52 twist=33.1

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List of 2 G4-stems

In DSSR, a G4-stem is defined as a G4-helix with backbone connectivity. Bulges are also allowed along each of the four strands.

Stem#1, 2 G-tetrad layers, 3 loops, INTRA-molecular, UUUU, parallel, 2(-P-P-P), parallel(4+0)

 1  glyco-bond=---- sugar=-333 groove=---- WC-->Major nts=4 GGGG B.G20,B.G24,B.G29,B.G32
 2  glyco-bond=---- sugar=33-3 groove=---- WC-->Major nts=4 GGGG B.G21,B.G25,B.G30,B.G33
  step#1  pm(>>,forward)  area=11.59 rise=3.40 twist=29.7
  strand#1  U RNA glyco-bond=-- sugar=-3 nts=2 GG B.G20,B.G21
  strand#2  U RNA glyco-bond=-- sugar=33 nts=2 GG B.G24,B.G25
  strand#3  U RNA glyco-bond=-- sugar=3- nts=2 GG B.G29,B.G30
  strand#4  U RNA glyco-bond=-- sugar=33 nts=2 GG B.G32,B.G33
  loop#1 type=propeller strands=[#1,#2] nts=2 GU B.G22,B.U23
  loop#2 type=propeller strands=[#2,#3] nts=3 UGU B.U26,B.G27,B.U28
  loop#3 type=propeller strands=[#3,#4] nts=1 A B.A31

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Stem#2, 2 G-tetrad layers, 3 loops, INTRA-molecular, UUUU, parallel, 2(-P-P-P), parallel(4+0)

 1  glyco-bond=---- sugar=-333 groove=---- WC-->Major nts=4 GGGG A.G20,A.G24,A.G29,A.G32
 2  glyco-bond=---- sugar=33-3 groove=---- WC-->Major nts=4 GGGG A.G21,A.G25,A.G30,A.G33
  step#1  pm(>>,forward)  area=11.39 rise=3.43 twist=30.4
  strand#1  U RNA glyco-bond=-- sugar=-3 nts=2 GG A.G20,A.G21
  strand#2  U RNA glyco-bond=-- sugar=33 nts=2 GG A.G24,A.G25
  strand#3  U RNA glyco-bond=-- sugar=3- nts=2 GG A.G29,A.G30
  strand#4  U RNA glyco-bond=-- sugar=33 nts=2 GG A.G32,A.G33
  loop#1 type=propeller strands=[#1,#2] nts=2 GU A.G22,A.U23
  loop#2 type=propeller strands=[#2,#3] nts=3 UGU A.U26,A.G27,A.U28
  loop#3 type=propeller strands=[#3,#4] nts=1 A A.A31

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List of 1 G4 coaxial stack

 1 G4 helix#1 contains 2 G4 stems: [#1,#2]  [5'/5']