9I2I: Immunoglobulin G-binding protein G

X-ray structure of the B1 domain of streptococcal protein G triple mutant T2Q, N8D, and N37D (GB1-QDD). Determined by X-ray diffraction at 1.08 Å resolution. Released 3 Sept 2025.

Method: X-ray diffraction
Resolution: 1.08 Å
Organism: Streptococcus sp.
Chains: 2
Atoms: 1,050
Mol. weight: 12.48 kDa
Released: 3 Sept 2025

Explore 9I2I in 3D Show helices and sheets RCSB PDB PDBe

Secondary structure: helices and β-sheets

9I2I contains 4 α-helices and 8 β-strands across 2 chains. Residue ranges use author residue numbering, as in the PDB file, from PDBe. To see them in 3D, choose the Cartoon representation with Secondary structure coloring: helices, sheets and coils get different colors.

Chain A: 2 helices, 4 β-strands

Element	Residues	Length	Sheet
β-strand	2-8	7	1
β-strand	12-19	8	1
α-helix	23-36	14
β-strand	42-46	5	1
α-helix	47-49	3
β-strand	51-55	5	1

Chain B: 2 helices, 4 β-strands

Element	Residues	Length	Sheet
β-strand	2-8	7	1
β-strand	12-19	8	1
α-helix	23-35	13
β-strand	42-46	5	1
α-helix	47-49	3
β-strand	51-55	5	1

Molecules and chains

Molecule	Chains	Type	Length	Organism	UniProt
Immunoglobulin G-binding protein G	A, B	protein	56	Streptococcus sp.	P19909 (AlphaFold model)

Sequence of entity 1 (A, B), FASTA

>9I2I_1 Immunoglobulin G-binding protein G (chains A, B)
MQYKLILDGKTLKGETTTEAVDAATAEKVFKQYANDDGVDGEWTYDDATKTFTVTE

Primary citation

Aromatic ring flips reveal reshaping of protein dynamics in crystals and complexes. Becker, L.M., Fu, H., Tatman, B.P. et al. Nat Chem (2026) 18:1221-1230. DOI 10.1038/s41557-026-02155-0 · PubMed

Other PDB entries of the same protein (UniProt P19909 (AlphaFold model), which also has an AlphaFold model), best resolution first:

3FIL 0.88 Å, Structural and energetic determinants for hyperstable variants of GB1 obtained from…
2QMT 1.05 Å, Crystal Polymorphism of Protein GB1 Examined by Solid-state NMR and X-ray Diffraction
6CHE 1.1 Å, Selenomethionine mutant (A34Sem) of protein GB1 examined by X-ray diffraction
6CPZ 1.12 Å, Selenomethionine mutant (I6Sem) of protein GB1 examined by X-ray diffraction
2GI9 1.14 Å, Backbone Conformational Constraints in a Microcrystalline U-15N-Labeled Protein by 3D…
6C9O 1.2 Å, Selenomethionine mutant (V29Sem) of protein GB1 examined by X-ray diffraction
6CTE 1.2 Å, 77Se-NMR probes the protein environment of selenomethionine
6OC7 1.3 Å, HMP42 Fab in complex with Protein G
6NLA 1.34 Å, Crystal structure of de novo designed metal-controlled dimer of B1…
2ON8 1.35 Å, Gbeta1 stabilization by in vitro evolution and computational design
12LO 1.37 Å, X-ray crystal structure of Protein GB1 mutant K13A
6NL6 1.4 Å, Crystal structure of mutant B1 immunoglobulin-binding domain of Streptococcal Protein G…

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