The structures of secretory and dimeric immunoglobulin A
- Department of Biochemistry, University of Illinois Urbana-Champaign, United States
- Division of Biology and Biological Engineering, California Institute of Technology, United States
- Beckman Institute, California Institute of Technology, United States
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana–Champaign, United States
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, United States
Figures
Figure 1 with 1 supplement
SIgA delivery to the mucosa.
(A) Schematic depicting unliganded pIgR binding to dIgA from the lamina propria on the basolateral surface of an epithelial cell followed by transcytosis to the apical membrane and SIgA release into …
Figure 1—figure supplement 1
Sequence identity, similarity, and alignments between mouse and human SIgA components.
(A) Sequence identity and similarity calculated between the indicated mouse and human sequences. (B) Sequences of the mouse SIgA structure components aligned to homologous human sequences. The …
Figure 2 with 4 supplements
SIgA structure.
(A) Schematic representing ordered domains in the SIgA structure. The relative position of each SIgA component is approximated based on the structure. Chain IDs and corresponding CH domains and Fcs …
Figure 2—figure supplement 1
SIgA cryoEM data collection and CryoSparc processing pipeline.
(A) Schematic summary of the data processing pipeline of SIgA reconstruction in cryoSparc2. (B) Representative micrograph (scale bar – 50 nm) and (C) 2D class averages. (D) Local resolution map of …
Figure 2—figure supplement 2
SIgA cryoEM data collection and Relion processing pipeline.
(A) Schematic summary of the data processing pipeline of SIgA reconstruction in Relion. (B) Representative 2D class averages. (C) FSC curve for the final reconstruction with reported resolution at …
Figure 2—figure supplement 3
SIgA cross-validation FSC curves.
The FSC curve generated between the final structure and CryoEM map including all data (FSCmap-model) is shown in black and indicates agreement between the map and final model. FSCwork (red) is the …
Figure 2—figure supplement 4
SIgA glycosylation.
Cartoon representations of SIgA structure with ordered glycosylation shown as sticks. The structure is shown in four orientations and colored as in Figure 2.
Figure 3
Fc dimer interface and JC structure.
(A) Schematic depicting the topology that arises from JC and its interactions with four Tps and colored as in Figure 2. JC regions (JCW1, JCW2, JCcore, and N- and C termini) are labeled along with …
Figure 4
SC Structure.
(A) Cartoon representations of an unliganded mouse SC homology model based on unliganded human SC crystal structure (PDB code 5D4K; left) and the dIgA-bound mouse SC (right). The dIgA is shown as a …
Figure 5 with 2 supplements
dIgA structure.
(A) Cartoon representation (with semi-transparent molecular surface) of the unliganded dIgA structure shown in two orientations and colored as in Figure 2. The bend and tilt between the two Fcs is …
Figure 5—figure supplement 1
dIgA cryoEM data collection and processing strategy.
(A) Schematic summary of the data processing pipeline of dIgA reconstruction in cryoSparc2. (B) Representative micrograph (scale bar – 50 nm) and (C) 2D class averages. (D) Local resolution map of …
Figure 5—figure supplement 2
dIgA cross-validation FSC curves.
The FSC curve generated between the final structure and CryoEM map including all data (FSCmap-model) is shown in black and indicates agreement between the map and final model. FSCwork (red) is the …
Figure 6 with 1 supplement
Modeling of Fabs and CDRs on SIgA.
(A) SIgA structure shown with four Fabs, each modeled in a single position as well as all possible positions and shown in multiple orientations. Complex components are colored according to the key …
Figure 6—figure supplement 1
Modeling strategy for the computational search of SIgA Fab positions.
(Left) SIgA structure shown with four modeled Fabs in one orientation. (Right) Schematic showing how Fab positions were modeled by mapping a vector, spanning from the N-terminal residue in the CH2 …
Figure 7
Model for the formation, transport,and function of SIgA.
Schematic summary depicting the unliganded SC structure (pdb code 5D4K) as pIgR bound to basolateral surface of an epithelial cell in its closed conformation and recognizing bent dIgA from the …
Tables
Key resources table
| Reagent type (species) or resource | Designation | Source or reference | Identifiers | Additional information |
|---|---|---|---|---|
| Other | IGHA_MOUSE | UniProtKB RRID:SCR_004426 | UniProtKB: P01878 | Amino acid sequence of Mus musculus IgA heavy chain constant regions |
| Other | LAC1_MOUSE | UniProtKB RRID:SCR_004426 | UniProtKB: P01843 | Amino acid sequence of Mus musculus lambda-1 light chain constant region |
| Other | IGJ_MOUSE | UniProtKB RRID:SCR_004426 | UniProtKB: P01592 | Amino acid sequence of Mus musculus joining chain |
| Other | PIGR_MOUSE | UniProtKB RRID:SCR_004426 | UniProtKB: O70570 | Amino acid sequence of Mus musculus polymeric Ig Receptor |
| Other | STA121 | Moor et al., 2017 | Variable region of human IgA2 antibody STA121 | |
| Cell line (Homo sapiens) | HEK Expi293F | Thermo Fisher RRID:SCR_008452 | Cat#: A14635 RRID:CVCL_D615 | |
| Recombinant DNA reagent | pD2610-v1 | ATUM | Cat#: pD2610-v1-03 | Mammalian expression plasmid |
| Transfected construct (Homo sapiens) | STA121 IgA Heavy chain (HC) in pD2610v1 | Materials and methods of this paper | Construct encoding STA121 heavy chain (HC) variable region fused to Mus musculus IgA HC constant domains | |
| Transfected construct (Homo sapiens) | STA121 IgA light chain (LC) lambda in pD2610v1 | Materials and methods of this paper | Construct encoding STA121 light chain (LC) variable region fused to Mus musculus lambda LC constant domain | |
| Transfected construct (Homo sapiens) | Mouse Secretory component (SC) in pD2610v1 | Materials and methods of this paper | Construct encoding residues 1–567 of Mus musculus pIgR (a.k.a. secretory component; SC) | |
| Transfected construct (Homo sapiens) | Mouse joining chain (JC) in pD2610v1 | Materials and methods of this paper | Construct encoding Mus musculus joining chain (JC) | |
| Peptide, recombinant protein | STA121 Secretory IgA | Materials and methods of this paper | Protein complex produced from transfected constructs and containing: STA121 HC, STA121 LC, JC, SC | |
| Peptide, recombinant protein | STA121 dimeric IgA | Materials and methods of this paper | Protein complex produced from transfected constructs and containing: STA121 HC, STA121 LC, JC | |
| Other | CaptureSelect LC-lambda (Mouse) Affinity Matrix | Thermo Fisher RRID:SCR_008452 | Cat#: 194323005 | Affinity matrix for protein purification |
| Other | Superose 6 Increase 10/300 GL | GE Healthcare Life Sciences RRID:SCR_000004 | Cat#: 29091596 | Size exclusion column for protein purification |
| Software, algorithm | Rosetta CryoEM refinement package | Wang et al., 2016 | RRID:SCR_015701 | |
| Software, algorithm | Phenix | Afonine et al., 2018a; Afonine et al., 2018b | Phenix RRID:SCR_014224 Phenix.refine RRID:SCR_016736 | |
| Software, algorithm | Pymol Molecular Graphics System | Schrodinger LLC RRID:SCR_014879 | RRID:SCR_000305 | |
| Software, algorithm | RELION-3 | Scheres, 2012; Zivanov et al., 2018 | RRID:SCR_016274 | |
| Software, algorithm | UCSF Chimera | Pettersen et al., 2004; Yang et al., 2012 | RRID:SCR_004097 | |
| Software, algorithm | UCSF ChimeraX | Goddard et al., 2018 | RRID:SCR_015872 | |
| Software, algorithm | cryoSPARC v.2 | Punjani et al., 2017 | RRID:SCR_016501 | |
| Software, algorithm | VMD | Humphrey et al., 1996 | RRID:SCR_001820 |
Additional files
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Supplementary file 1
CryoEM data collection and refinement statistics associated with SIgA and dIgA structures.
- https://cdn.elifesciences.org/articles/56098/elife-56098-supp1-v2.xlsx
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Transparent reporting form
- https://cdn.elifesciences.org/articles/56098/elife-56098-transrepform-v2.docx
