Structure of S. aureus protein A bound to a human IgM Fab
Domain Annotation: SCOP/SCOPe Classification SCOP-e Database Homepage
Domain Annotation: ECOD Classification ECOD Database Homepage
| Chains | Family Name | Domain Identifier | Architecture | Possible Homology | Homology | Topology | Family | Provenance Source (Version) |
|---|---|---|---|---|---|---|---|---|
| C | C1-set_4 | e1deeC2 | A: beta sandwiches | X: Immunoglobulin-like beta-sandwich | H: Immunoglobulin-related | T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like | F: C1-set_4 | ECOD (1.6) |
| C | V-set | e1deeC1 | A: beta sandwiches | X: Immunoglobulin-like beta-sandwich | H: Immunoglobulin-related | T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like | F: V-set | ECOD (1.6) |
| E | C1-set_4 | e1deeE2 | A: beta sandwiches | X: Immunoglobulin-like beta-sandwich | H: Immunoglobulin-related | T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like | F: C1-set_4 | ECOD (1.6) |
| E | V-set | e1deeE1 | A: beta sandwiches | X: Immunoglobulin-like beta-sandwich | H: Immunoglobulin-related | T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like | F: V-set | ECOD (1.6) |
| A | C1-set_4 | e1deeA2 | A: beta sandwiches | X: Immunoglobulin-like beta-sandwich | H: Immunoglobulin-related | T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like | F: C1-set_4 | ECOD (1.6) |
| A | V-set | e1deeA1 | A: beta sandwiches | X: Immunoglobulin-like beta-sandwich | H: Immunoglobulin-related | T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like | F: V-set | ECOD (1.6) |
| B | V-set_8 | e1deeB1 | A: beta sandwiches | X: Immunoglobulin-like beta-sandwich | H: Immunoglobulin-related | T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like | F: V-set_8 | ECOD (1.6) |
| B | C1-set_1 | e1deeB2 | A: beta sandwiches | X: Immunoglobulin-like beta-sandwich | H: Immunoglobulin-related | T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like | F: C1-set_1 | ECOD (1.6) |
| D | V-set_8 | e1deeD1 | A: beta sandwiches | X: Immunoglobulin-like beta-sandwich | H: Immunoglobulin-related | T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like | F: V-set_8 | ECOD (1.6) |
| D | C1-set_1 | e1deeD2 | A: beta sandwiches | X: Immunoglobulin-like beta-sandwich | H: Immunoglobulin-related | T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like | F: C1-set_1 | ECOD (1.6) |
| F | V-set_8 | e1deeF1 | A: beta sandwiches | X: Immunoglobulin-like beta-sandwich | H: Immunoglobulin-related | T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like | F: V-set_8 | ECOD (1.6) |
| F | C1-set_1 | e1deeF2 | A: beta sandwiches | X: Immunoglobulin-like beta-sandwich | H: Immunoglobulin-related | T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like | F: C1-set_1 | ECOD (1.6) |
| G | B | e1deeG1 | A: alpha bundles | X: immunoglobulin/albumin-binding domain-like | H: Bacterial immunoglobulin/albumin-binding domains (From Topology) | T: Bacterial immunoglobulin/albumin-binding domains | F: B | ECOD (1.6) |
| H | B | e1deeH1 | A: alpha bundles | X: immunoglobulin/albumin-binding domain-like | H: Bacterial immunoglobulin/albumin-binding domains (From Topology) | T: Bacterial immunoglobulin/albumin-binding domains | F: B | ECOD (1.6) |
Domain Annotation: CATH CATH Database Homepage
| Chain | Domain | Class | Architecture | Topology | Homology | Provenance Source (Version) |
|---|---|---|---|---|---|---|
| C | 2.60.40.10 | Mainly Beta | Sandwich | Immunoglobulin-like | Immunoglobulins | CATH (4.3.0) |
| E | 2.60.40.10 | Mainly Beta | Sandwich | Immunoglobulin-like | Immunoglobulins | CATH (4.3.0) |
| A | 2.60.40.10 | Mainly Beta | Sandwich | Immunoglobulin-like | Immunoglobulins | CATH (4.3.0) |
| B | 2.60.40.10 | Mainly Beta | Sandwich | Immunoglobulin-like | Immunoglobulins | CATH (4.3.0) |
| D | 2.60.40.10 | Mainly Beta | Sandwich | Immunoglobulin-like | Immunoglobulins | CATH (4.3.0) |
| F | 2.60.40.10 | Mainly Beta | Sandwich | Immunoglobulin-like | Immunoglobulins | CATH (4.3.0) |
| G | 1.20.5.420 | Mainly Alpha | Up-down Bundle | Single alpha-helices involved in coiled-coils or other helix-helix interfaces | Immunoglobulin FC, subunit C | CATH (4.3.0) |
| H | 1.20.5.420 | Mainly Alpha | Up-down Bundle | Single alpha-helices involved in coiled-coils or other helix-helix interfaces | Immunoglobulin FC, subunit C | CATH (4.3.0) |
IMGT Antibody Annotation IMGT Database Homepage
| Chain | Protein Name | Description | Organism Name | Gene Allele Name(s) | Domain Name(s) | Receptor Type | Receptor Description | Provenance Source |
|---|---|---|---|---|---|---|---|---|
| IgmRf2A2 | L-KAPPA | Homo sapiens (human) | IGKV1-39*01, IGKV1D-39*01, IGKJ1*01, IGKC*01 | V-DOMAIN V-KAPPA, C-DOMAIN C-KAPPA | IG | FAB-MU_KAPPA | IMGT (202542-0) | |
| IgmRf2A2 | VH-CH1 | Homo sapiens (human) | IGHV3-30*18, IGHJ4*01, IGHJ4*02, IGHJ4*03, IGHM*03 | V-DOMAIN VH, C-DOMAIN CH1 | IG | FAB-MU_KAPPA | IMGT (202542-0) |
SAbDab Antibody Annotation SAbDab Database Homepage
| Chain | Chain Class | Chain Subclass | Chain Type | Antigen Name(s) | Provenance Source |
|---|---|---|---|---|---|
| Light Chain | IGKV1 | Kappa | immunoglobulin g binding protein a | SAbDab (2025-10-31) | |
| Heavy Chain | IGHV3 | - | immunoglobulin g binding protein a | SAbDab (2025-10-31) |
Protein Family Annotation Pfam Database Homepage
| Chains | Accession | Name | Description | Comments | Source |
|---|---|---|---|---|---|
| PF02216 | B domain (B) | B domain | This family contains the B domain of Staphylococcal protein A, which specifically binds to the Fc portion of immunoglobulin G. | Domain |
Gene Ontology: Gene Product Annotation Gene Ontology Database Homepage
InterPro: Protein Family Classification InterPro Database Homepage
| Chains | Accession | Name | Type |
|---|---|---|---|
| IPR009063 | Immunoglobulin/albumin-binding domain superfamily | Homologous Superfamily | |
| IPR005877 | YSIRK Gram-positive signal peptide | Domain | |
| IPR036779 | LysM domain superfamily | Homologous Superfamily | |
| IPR005038 | Octapeptide repeat | Repeat | |
| IPR003132 | Protein A, Ig-binding domain | Domain | |
| IPR018392 | LysM domain | Domain | |
| IPR019931 | LPXTG cell wall anchor domain | Domain |














