26SG | pdb_000026sg

Sunflower protein amyloid fibrils

• PDB DOI: https://doi.org/10.2210/pdb26SG/pdb
• EM Map EMD-80851: EMDB EMDataResource

• Classification: PROTEIN FIBRIL
• Organism(s): Helianthus annuus
• Expression System: Helianthus annuus
• Mutation(s): No 


• Deposited: 2026-05-13 Released: 2026-10-07 
• Deposition Author(s): Li, S., Cao, Q., Cao, Y.
• Funding Organization(s): National Natural Science Foundation of China (NSFC)

---

Experimental Data Snapshot

• Method: ELECTRON MICROSCOPY
• Resolution: 3.05 Å
• Aggregation State: PARTICLE 
• Reconstruction Method: HELICAL 

Literature

Cryo-EM Structures of Sunflower Amyloid Fibrils Reveal Two Distinct Disulfide‐Linked Assembly Modes.

Li, S., Ouyang, K., Li, S., Fang, Y., Cao, Q., Cao, Y.

(2026) Small : e75987-e75987

• PubMed: 42801496 
• DOI: https://doi.org/10.1002/smll.75987
• Primary Citation Related Structures: 
  26SG, 44ZG


• PubMed Abstract: 
  

  Sunflower meal is an abundant but underutilized plant protein source. Recent studies have demonstrated that its amyloid fibrils exhibit exceptional functional properties, yet the atomic-level structural basis remains unknown. The first cryo‑electron microscopy (cryo‑EM) structures of sunflower amyloid fibrils prepared under acidic heating conditions are presented. Two distinct polymorphs (PM1 and PM2) are resolved at 3.05 and 3.18 Å, respectively. They differ markedly in both helical half-pitch (389 Å for PM1 vs. 1087 Å for PM2) and handedness (left-handed for PM1 vs. right-handed for PM2). High-resolution atomic modeling reveals that they adopt distinct assembly modes. PM1 is assembled from the acidic (Leu94-Phe115) and basic (Val333-Phe344) subunits of 11S globulin, covalently linked by an inter-subunit disulfide bond (Cys111-Cys338); whereas PM2 is formed by an acidic-subunit segment (Asn30-Val68) and stabilized by an intra-subunit disulfide bond (Cys32-Cys65). Comparison of the PM1 structure with the apricot globulin fibril reveals divergent assembly strategies, most strikingly an opposite orientation of the basic subunit relative to the acidic fragment despite high sequence homology. These structural insights provide a molecular foundation for understanding and engineering sunflower amyloid fibrils for diverse applications in food, agriculture, and nanotechnology.

---

Organizational Affiliation: 
• Department of Food Science & Engineering, School of Agriculture & Biology, Shanghai Jiao Tong University, Shanghai, China.
School of Health Science & Engineering, University of Shanghai for Science and Technology, Shanghai, China.
Bio-X Institutes, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders, Ministry of Education, Shanghai Jiao Tong University, Shanghai, China.

Biological Assembly 1  

Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Homo 5-mer - A5 

Biological assembly 1 assigned by authors and generated by (software)

Biological Assembly Evidence: electron microscopy

Macromolecule Content 

• Total Structure Weight: 142.71 kDa 
• Atom Count: 1,275 
• Modeled Residue Count: 170 
• Deposited Residue Count: 1,255 
• Unique protein chains: 1

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
11-S seed storage protein, plant	A, B, C, D, E	251	Helianthus annuus	Mutation(s): 0  Gene Names: HanXRQr2_Chr04g0170751
UniProt
Find proteins for A0A9K3J848 (Helianthus annuus) Explore A0A9K3J848  Go to UniProtKB:  A0A9K3J848

Experimental Data & Validation

Experimental Data

• Method: ELECTRON MICROSCOPY
• Resolution: 3.05 Å
• Aggregation State: PARTICLE 
• Reconstruction Method: HELICAL 

EM Software:

Task	Software Package	Version
MODEL REFINEMENT	PHENIX
RECONSTRUCTION	RELION	4.0

Structure Validation

Entry History 

& Funding Information

Deposition Data

• Released Date: 2026-10-07 
Deposition Author(s): Li, S., Cao, Q., Cao, Y.

---

Funding Organization	Location	Grant Number
National Natural Science Foundation of China (NSFC)	China	32572505

Revision History  

• Version 1.0: 2026-10-07
  Type: Initial release