7RAW

Domain 1 of Starch adherence system protein 20 (Sas20) from Ruminococcus bromii


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.10 Å
  • R-Value Free: 0.214 
  • R-Value Work: 0.177 
  • R-Value Observed: 0.180 

wwPDB Validation   3D Report Full Report


This is version 1.1 of the entry. See complete history


Literature

Sas20 is a highly flexible starch-binding protein in the Ruminococcus bromii cell-surface amylosome.

Cerqueira, F.M.Photenhauer, A.L.Doden, H.L.Brown, A.N.Abdel-Hamid, A.M.Morais, S.Bayer, E.A.Wawrzak, Z.Cann, I.Ridlon, J.M.Hopkins, J.B.Koropatkin, N.M.

(2022) J Biol Chem 298: 101896-101896

  • DOI: 10.1016/j.jbc.2022.101896
  • Primary Citation of Related Structures:  
    7RAW, 7RFT, 7RPY

  • PubMed Abstract: 
  • Ruminococcus bromii is a keystone species in the human gut that has the rare ability to degrade dietary resistant starch (RS). This bacterium secretes a suite of starch-active proteins that work together within larger complexes called amylosomes that allow R ...

    Ruminococcus bromii is a keystone species in the human gut that has the rare ability to degrade dietary resistant starch (RS). This bacterium secretes a suite of starch-active proteins that work together within larger complexes called amylosomes that allow R. bromii to adhere to and degrade RS. Sas20 is one of the more abundant proteins assembled within amylosomes, but little could be predicted about its molecular features based on amino acid sequence alone. Here, we performed a structure-function analysis of Sas20 and determined that it features two discrete starch-binding domains separated by a flexible linker. We show Sas20 domain 1 contains an N-terminal β-sandwich followed by a cluster of α-helices, and the non-reducing end of maltooligosaccharides can be captured between these structural features. Furthermore, the crystal structure of a close homolog of Sas20 domain 2 revealed a unique bi-lobed starch-binding groove that targets the helical α1,4-linked glycan chains found in amorphous regions of amylopectin and crystalline regions of amylose within starch granules. Affinity PAGE and isothermal titration calorimetry demonstrated that both domains bind maltoheptaose and soluble starch with relatively high affinity (K d ≤ 20 μM) but exhibit limited or no binding to cyclodextrins. Finally, small angle x-ray scattering analysis of the individual and combined domains support that these structures are highly flexible, which may allow the protein to adopt conformations that enhance its starch-targeting efficiency. Taken together, we conclude that Sas20 binds distinct features within the starch granule, facilitating the ability of R. bromii to hydrolyze dietary resistant starch.


    Organizational Affiliation

    Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109, USA. Electronic address: nkoropat@umich.edu.



Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
Dockerin domain-containing proteinA251Ruminococcus bromii L2-63Mutation(s): 0 
Gene Names: RBL236_01231
UniProt
Find proteins for A0A2N0URA4 (Ruminococcus bromii)
Explore A0A2N0URA4 
Go to UniProtKB:  A0A2N0URA4
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupA0A2N0URA4
Protein Feature View
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  • Reference Sequence
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
PGE
Query on PGE

Download Ideal Coordinates CCD File 
C [auth A]TRIETHYLENE GLYCOL
C6 H14 O4
ZIBGPFATKBEMQZ-UHFFFAOYSA-N
 Ligand Interaction
PEG
Query on PEG

Download Ideal Coordinates CCD File 
B [auth A]DI(HYDROXYETHYL)ETHER
C4 H10 O3
MTHSVFCYNBDYFN-UHFFFAOYSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.10 Å
  • R-Value Free: 0.214 
  • R-Value Work: 0.177 
  • R-Value Observed: 0.180 
  • Space Group: I 21 3
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 130.032α = 90
b = 130.032β = 90
c = 130.032γ = 90
Software Package:
Software NamePurpose
HKL-2000data scaling
PHENIXrefinement
PDB_EXTRACTdata extraction
HKL-2000data reduction
PHENIXphasing

Structure Validation

View Full Validation Report




Entry History & Funding Information

Deposition Data


Funding OrganizationLocationGrant Number
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)United StatesF31 GM137488

Revision History  (Full details and data files)

  • Version 1.0: 2022-04-13
    Type: Initial release
  • Version 1.1: 2022-05-25
    Changes: Database references