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Center for Structural Genomics of Infectious Diseases

MgRNA: Classification of Mg2+ binding sites in RNA crystal structures
Mg2+ site A1577 in 2QBH (4Å) -- RIBOSOME : Crystal structure of the bacterial ribosome from escherichia coli in complex with gentamicin and ribosome recycling factor (rrf). this file contains the 30s subunit of the first 70s ribosome, with gentamicin bound. the entire crystal structure contains

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Binding environment of Mg2+ A1577

Site type*

cis-2Oph·2Ob

Coordination Number 6
Qv # 0.69
Qs # 0.54
Qe # 1.00
 
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Inner-sphere Residue Name:
Outer-sphere Moiety Name:
Metal Distances:
Outer-sphere Distances:
B factor(Occupancy):
Nucleic Acid Cartoon:
Spin:
Antialiasing:		 On Off
On Off
On Off
On Off
On Off
On Off
On Off
On Off

# Validation parameters Qv, Qs, Qe are defined in the range of 0 to 1, with 0 indicating poorest reliability and higher value indicating a more reliable site
Qv measures the agreement of the inner-sphere bond valence summation with the oxidation state of Mg2+ (+2)
Qs measures the geometrical symmetry of the ligands distribution around the Mg2+ required for octahedral geometry
Qe measures the agreement of the isotropic atomic displacement (B) factor and occupancy of the Mg2+ compared to those of all atoms in its environment

Site type used in the classification is a string abbreviation of ligand composition in Mg2+ coordination sphere
Abbreviations
used for Mg2+
"Site type"		 Mg2+ inner-sphere ligands Geometry for inner-sphere OP Mg2+ outer-sphere moieties
Oph phosphate oxygen (OP1/OP2)
Or ribose oxygen (O2'/O4')
     or oxygen bridging phosphate and ribose (O3'/O5')
Ob nucleobase oxygen      Nb nucleobase nitrogen 		cis- two OP ligands adopt cis- isoform
trans- two OP ligands adopt trans- isoform
fac- three OP ligands adopt fac- isoform
mer- three OP ligands adopt mer- isoform 		Pout phosphate moiety
Rout ribose moiety
Bout nucleobase moiety
Reference: Zheng H, Shabalin IG, Handing KB, Bujnicki JM, Minor W. (2015) Magnesium binding architectures in RNA crystal structures: validation, binding preferences, classification, and motif detection. Nucleic Acid Research 43(7):3789-801 [Pubmed].

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