9ROB: Human CD22 Ig domains 1-3

Crystal structure of human CD22 Ig domains 1-3 in complex with modified sialoside 1B. Determined by X-ray diffraction at 2.7 Å resolution. Released 10 Dec 2025.

Method: X-ray diffraction
Resolution: 2.7 Å
Organism: Homo sapiens
Chains: 2
Atoms: 4,979
Mol. weight: 76.06 kDa
Ligands: A1JJN
Released: 10 Dec 2025

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

Secondary structure: helices and β-sheets

9ROB contains 9 α-helices and 61 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: 4 helices, 30 β-strands

Element	Residues	Length	Sheet
β-strand	24-27	4	1
β-strand	31-35	5	2
β-strand	40-42	3	3
β-strand	45-48	4	1
β-strand	55-65	11	2
β-strand	70-78	9	2
β-strand	92-94	3	3
β-strand	101	1	1
β-strand	104-106	3	3
α-helix	111-113	3
β-strand	115-122	8	2
β-strand	127-137	11	2
α-helix	140-142	3
β-strand	144-146	3	4
β-strand	151-152	2	5
β-strand	157-163	7	4
β-strand	172-178	7	6
β-strand	181-182	2	6
β-strand	187-193	7	4
β-strand	198-206	9	4
α-helix	210-212	3
β-strand	216-223	8	6
β-strand	228-235	8	6
β-strand	238-239	2	5
β-strand	240-248	9	7
β-strand	261-271	11	7
β-strand	274-280	7	8
β-strand	285	1	8
α-helix	286	1
β-strand	293-296	4	7
β-strand	306-307	2	9
β-strand	308-313	6	8
β-strand	317-319	3	8
β-strand	323-324	2	9

Chain B: 5 helices, 31 β-strands

Element	Residues	Length	Sheet
β-strand	25-27	3	10
β-strand	31-35	5	11
β-strand	40-42	3	12
β-strand	45-47	3	10
β-strand	55-65	11	11
β-strand	70-78	9	11
β-strand	92-94	3	12
β-strand	101	1	10
β-strand	104-106	3	12
α-helix	111-113	3
β-strand	115-122	8	11
β-strand	127-137	11	11
α-helix	140-142	3
β-strand	144-146	3	13
β-strand	151-152	2	14
β-strand	157-163	7	13
β-strand	172-178	7	15
β-strand	181-182	2	15
β-strand	187-193	7	13
β-strand	198-206	9	13
α-helix	207-209	3
α-helix	210-212	3
β-strand	216-223	8	15
β-strand	228-235	8	15
β-strand	238-239	2	14
β-strand	240-249	10	16
β-strand	254-255	2	17
β-strand	261-271	11	16
β-strand	276-281	6	18
β-strand	284-285	2	18
α-helix	286	1
β-strand	293-296	4	16
β-strand	306-312	7	18
β-strand	317-319	3	18
β-strand	323-324	2	18
β-strand	326-327	2	17

Molecules and chains

Molecule	Chains	Type	Length	Organism	UniProt
B-cell receptor CD22	A, B	protein	324	Homo sapiens	P20273 (AlphaFold model)

Sequence of entity 1 (A, B), FASTA

>9ROB_1 B-cell receptor CD22 (chains A, B)
ETGDSSKWVFEHPETLYAWEGACVWIPCTYRALDGDLESFILFHNPEYNKATSKFDGTRL
YESTKDGKVPSEQKRVQFLGDKNKNCTLSIHPVHLADSGQLGLRMESKTEKWMERIHLAV
SERPFPPHIQLPPEIQESQEVTLTCLLAFSCYGYPIQLQWLLEGVPMRQAAVTSTSLTIK
SVFTRSELKFSPQWSHHGKIVTCQLQDADGKFLSADTVQLNVKHTPKLEIKVTPSDAIVR
EGDSVTMTCEVSSSNPEYTTVSWLKDGTSLKKQNTFTLNLREVTKDQSGKYCCQVSNDVG
PGRSEEVFLQVQYAGGTKHHHHHH

Ligands and cofactors

ID	Name	Formula	Copies
A1JJN	(2R,4S,5R,6R)-5-acetamido-2-[[2,3-bis(chloranyl)phenyl]methoxy]-6-[(1R,2R)-1,2-…	C31 H32 Cl2 N2 O9	2

Water and common crystallization additives (GOL) are not listed.

Primary citation

Molecular Insights into the Engagement of High-Affinity Sialylated Ligands to Human CD22. Ereno-Orbea, J., Pang, L., Sicard, T. et al. JACS Au (2025) 5:5524-5537. DOI 10.1021/jacsau.5c01013 · PubMed

Other PDB entries of the same protein (UniProt P20273 (AlphaFold model), which also has an AlphaFold model), best resolution first:

5VKJ 2.12 Å, Crystal structure of human CD22 Ig domains 1-3
5VKM 2.2 Å, Crystal structure of human CD22 Ig domains 1-3 in complex with alpha 2-6 sialyllactose
7O52 2.41 Å, CD22 d6-d7 in complex with Fab m971
9RM3 2.86 Å, Crystal structure of human CD22 Ig domains 1-3 in complex with modified sialoside 17
5VL3 3.1 Å, CD22 d1-d3 in complex with therapeutic Fab Epratuzumab
9RO7 3.15 Å, Crystal structure of human CD22 Ig domains 1-3 in complex with modified sialoside 7-012

Browse structure collections

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