9R2E: ARGX-121 Fab fragment

Structure of ARGX-121 Fab fragment in complex with the Fc fragment of IgA1. Determined by X-ray diffraction at 2.54 Å resolution. Released 14 May 2025.

Method: X-ray diffraction
Resolution: 2.54 Å
Organism: Homo sapiens
Chains: 6
Atoms: 10,097
Mol. weight: 148.42 kDa
Ligands: MG
Released: 14 May 2025

Explore 9R2E in 3D Show helices and sheets RCSB PDB PDBe

Secondary structure: helices and β-sheets

9R2E contains 55 α-helices and 130 β-strands across 6 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: 8 helices, 23 β-strands

Element	Residues	Length	Sheet
β-strand	4-8	5	23
β-strand	12-13	2	24
β-strand	19-26	8	23
α-helix	30-32	3
β-strand	35-40	6	25
β-strand	46-52	7	25
β-strand	59-61	3	25
β-strand	70-74	5	23
β-strand	79-84	6	23
α-helix	89-91	3
β-strand	93-100	8	25
β-strand	106-109	4	25
β-strand	113-115	3	25
β-strand	116-117	2	24
β-strand	123	1	26
α-helix	124-125	2
β-strand	126-130	5	27
α-helix	131-133	3
β-strand	141-151	11	27
β-strand	152	1	26
β-strand	157-160	4	28
α-helix	161-163	3
β-strand	165	1	28
β-strand	169-171	3	27
α-helix	172-174	3
β-strand	175-176	2	27
β-strand	182-191	10	27
β-strand	201-206	6	28
α-helix	207-209	3
β-strand	211-216	6	28
α-helix	218-220	3

Chain B: 9 helices, 24 β-strands

Element	Residues	Length	Sheet
β-strand	4	1	29
β-strand	5	1	30
β-strand	9-12	4	31
β-strand	18-23	6	30
β-strand	35-40	6	31
α-helix	45-46	2
β-strand	47-51	5	31
β-strand	55-56	2	31
α-helix	57	1
β-strand	64-69	6	30
β-strand	72-77	6	30
α-helix	82-84	3
β-strand	87-93	7	31
β-strand	99-101	3	31
β-strand	102	1	29
β-strand	105-109	5	31
α-helix	112-114	3
β-strand	115	1	32
α-helix	116-117	2
β-strand	118-122	5	33
α-helix	123-125	3
α-helix	126-130	5
β-strand	134-143	10	33
β-strand	144	1	32
β-strand	149-154	6	34
β-strand	157-159	3	34
β-strand	163-165	3	33
α-helix	166-168	3
β-strand	169-170	2	33
β-strand	176-184	9	33
α-helix	186-190	5
β-strand	195-201	7	34
β-strand	204-210	7	34

Chain H: 8 helices, 23 β-strands

Element	Residues	Length	Sheet
β-strand	4-8	5	1
β-strand	12-13	2	2
β-strand	19-26	8	1
α-helix	30-32	3
β-strand	35-40	6	3
β-strand	46-52	7	3
β-strand	59-61	3	3
β-strand	69-74	6	1
β-strand	79-84	6	1
α-helix	89-91	3
β-strand	93-100	8	3
β-strand	106-109	4	3
β-strand	113-115	3	3
β-strand	116-117	2	2
β-strand	123	1	4
α-helix	124-125	2
β-strand	126-130	5	5
α-helix	131-133	3
β-strand	141-151	11	5
β-strand	152	1	4
β-strand	157-160	4	6
α-helix	161-163	3
β-strand	165	1	6
β-strand	169-171	3	5
α-helix	172-174	3
β-strand	175-176	2	5
β-strand	182-191	10	5
α-helix	192-194	3
β-strand	201-206	6	6
α-helix	207-209	3
β-strand	211-216	6	6

Chain L: 8 helices, 24 β-strands

Element	Residues	Length	Sheet
β-strand	4	1	7
β-strand	5	1	8
β-strand	9-12	4	9
β-strand	18-23	6	8
β-strand	35-40	6	9
β-strand	47-51	5	9
β-strand	55-56	2	9
α-helix	57	1
β-strand	64-69	6	8
β-strand	72-77	6	8
α-helix	82-84	3
β-strand	86-93	8	9
β-strand	99-101	3	9
β-strand	102	1	7
β-strand	105-109	5	9
α-helix	112-114	3
β-strand	115	1	10
α-helix	116-117	2
β-strand	118-122	5	11
α-helix	123-125	3
α-helix	126-130	5
β-strand	134-143	10	11
β-strand	144	1	10
β-strand	149-154	6	12
β-strand	157-159	3	12
β-strand	163-165	3	11
α-helix	166-168	3
β-strand	169-170	2	11
β-strand	176-184	9	11
α-helix	186-190	5
β-strand	195-201	7	12
β-strand	204-210	7	12

Chain P: 10 helices, 18 β-strands

Element	Residues	Length	Sheet
β-strand	246-249	4	13
α-helix	250-252	3
α-helix	253-258	6
β-strand	264-268	5	13
β-strand	278-281	4	14
β-strand	290-291	2	13
β-strand	304-308	5	13
α-helix	312-317	6
β-strand	321-322	2	15
β-strand	323-326	4	14
β-strand	334	1	14
β-strand	337-338	2	15
β-strand	348-352	5	16
α-helix	353-355	3
α-helix	356-361	6
β-strand	364-374	11	16
β-strand	380-385	6	17
β-strand	388-389	2	17
α-helix	390-391	2
α-helix	392-394	3
β-strand	396-397	2	16
α-helix	398-400	3
β-strand	401-402	2	16
α-helix	403-404	2
β-strand	411-420	10	16
α-helix	421-425	5
β-strand	430-435	6	17
β-strand	443-448	6	17

Chain Q: 12 helices, 18 β-strands

Element	Residues	Length	Sheet
β-strand	245-249	5	18
α-helix	250-252	3
α-helix	253-258	6
β-strand	264-269	6	18
β-strand	278-281	4	19
β-strand	290-295	6	18
β-strand	303-308	6	18
α-helix	312-317	6
α-helix	319-320	2
β-strand	321-322	2	20
β-strand	323-326	4	19
β-strand	334	1	19
β-strand	337-338	2	20
α-helix	346-347	2
β-strand	348-352	5	21
α-helix	353-355	3
α-helix	356-361	6
β-strand	364-374	11	21
β-strand	380-385	6	22
β-strand	388-389	2	22
α-helix	390-391	2
α-helix	392-394	3
β-strand	395-397	3	21
α-helix	398-400	3
β-strand	401-402	2	21
α-helix	403-404	2
β-strand	411-420	10	21
α-helix	421-426	6
β-strand	430-435	6	22
β-strand	443-448	6	22

Molecules and chains

Molecule	Chains	Type	Length	Organism	UniProt
ARGX-121 Fab fragment heavy chain	A, H	protein	244	Homo sapiens
ARGX-121 Fab fragment light chain	B, L	protein	235	Homo sapiens
Isoform 1 of Immunoglobulin heavy constant alpha 1	P, Q	protein	213	Homo sapiens	P01876 (AlphaFold model)

Sequence of entity 1 (A, H), FASTA

>9R2E_1 ARGX-121 Fab fragment heavy chain (chains A, H)
MGWSCIILFLVATATGVHSEVQLLESGGGLVQPGGSLRLSCAASGFTSSNYLMSWVRQAP
GKGLEWVSSIYHYGHNAYYADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKVDS
AYDFGSWGQGTLVTVSSASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNS
GALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSC
DKTH

Sequence of entity 2 (B, L), FASTA

>9R2E_2 ARGX-121 Fab fragment light chain (chains B, L)
MGWSCIILFLVATATGVHSQSVLTQPPSVSGAPGQRVTISCAGTSSDIGGRTYVSWYQQL
PGTAPKLLIYKVTIRASGVPDRFSGSKSGTSASLAITGLQAEDEADYYCASHRSNNNIVF
GGGTKLTVLGQPKAAPSVTLFPPSSEELQANKATLVCLISDFYPGAVTVAWKADSSPVKA
GVETTTPSKQSNNKYAASSYLSLTPEQWKSHRSYSCQVTHEGSTVEKTVAPTECS

Sequence of entity 3 (P, Q), FASTA

>9R2E_3 Isoform 1 of Immunoglobulin heavy constant alpha 1 (chains P, Q)
CHPRLSLHRPALEDLLLGSEANLTCTLTGLRDASGVTFTWTPSSGKSAVQGPPERDLCGC
YSVSSVLPGCAEPWNHGKTFTCTAAYPESKTPLTATLSKSGNTFRPEVHLLPPPSEELAL
NELVTLTCLARGFSPKDVLVRWLQGSQELPREKYLTWASRQEPSQGTTTFAVTSILRVAA
EDWKKGDTFSCMVGHEALPLAFTQKTIDRLAGK

Ligands and cofactors

ID	Name	Formula	Copies
MG	Magnesium ion	Mg	3

Water and common crystallization additives (EDO, PEG) are not listed.

Primary citation

Structure of ARGX-121 Fab fragment in complex with the Fc fragment of IgA1. Voet, S., Provost, M., Deweirdt, L. et al. To be published.

Other PDB entries of the same protein (UniProt P01876 (AlphaFold model), which also has an AlphaFold model), best resolution first:

9OFR 2.65 Å, Crystal structure of the human IGA1 fc fragment-fc-alpha receptor (CD89) complex
6UE7 2.9 Å, Structure of dimeric sIgA complex
1OW0 3.1 Å, Crystal structure of human FcaRI bound to IgA1-Fc
8SKV 3.1 Å, Structure of human SIgA1 in complex with Streptococcus pyogenes protein M4 (Arp4)
6LX3 3.15 Å, Cryo-EM structure of human secretory immunoglobulin A
2QEJ 3.2 Å, Crystal structure of a Staphylococcus aureus protein (SSL7) in complex with Fc of human…
8SKU 3.2 Å, Structure of human SIgA1 in complex with human CD89 (FcaR1)
6LXW 3.27 Å, Cryo-EM structure of human secretory immunoglobulin A in complex with the N-terminal…
9MBZ 3.3 Å, Cryo-EM structure of human FcRL4 bound to IgA-Fc/J
7UVL 3.56 Å, IgA1 Protease with IgA1 substrate
6XJA 4.0 Å, Streptococcus Pneumoniae IgA1 Protease with IgA1 substrate
1IGA Model of human IGA1 determined by solution scattering curve-fitting and homology modelling

Browse structure collections

About this viewer

MolViewer shows 9R2E directly in your browser with nothing to install. Switch between cartoon, ball-and-stick, spacefill and surface views, color by chain, secondary structure or B-factor, measure distances, angles and dihedrals, and share or embed the view.