1DF8

S45A MUTANT OF STREPTAVIDIN IN COMPLEX WITH BIOTIN


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.51 Å
  • R-Value Free: 0.225 
  • R-Value Work: 0.169 
  • R-Value Observed: 0.162 

Starting Model: experimental
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This is version 1.4 of the entry. See complete history


Literature

Ser45 plays an important role in managing both the equilibrium and transition state energetics of the streptavidin-biotin system.

Hyre, D.E.Le Trong, I.Freitag, S.Stenkamp, R.E.Stayton, P.S.

(2000) Protein Sci 9: 878-885

  • DOI: https://doi.org/10.1110/ps.9.5.878
  • Primary Citation of Related Structures:  
    1DF8

  • PubMed Abstract: 

    The contribution of the Ser45 hydrogen bond to biotin binding activation and equilibrium thermodynamics was investigated by biophysical and X-ray crystallographic studies. The S45A mutant exhibits a 1,700-fold greater dissociation rate and 907-fold lower equilibrium affinity for biotin relative to wild-type streptavidin at 37 degrees C, indicating a crucial role in binding energetics. The crystal structure of the biotin-bound mutant reveals only small changes from the wild-type bound structure, and the remaining hydrogen bonds to biotin retain approximately the same lengths. No additional water molecules are observed to replace the missing hydroxyl, in contrast to the previously studied D128A mutant. The equilibrium deltaG degrees, deltaH degrees, deltaS degrees, deltaC degrees(p), and activation deltaG++ of S45A at 37 degrees C are 13.7+/-0.1 kcal/mol, -21.1+/-0.5 kcal/mol, -23.7+/-1.8 cal/mol K, -223+/-12 cal/mol K, and 20.0+/-2.5 kcal/mol, respectively. Eyring analysis of the large temperature dependence of the S45A off-rate resolves the deltaH++ and deltaS++ of dissociation, 25.8+/-1.2 kcal/mol and 18.7+/-4.3 cal/mol K. The large increases of deltaH++ and deltaS++ in the mutant, relative to wild-type, indicate that Ser45 could form a hydrogen bond with biotin in the wild-type dissociation transition state, enthalpically stabilizing it, and constraining the transition state entropically. The postulated existence of a Ser45-mediated hydrogen bond in the wild-type streptavidin transition state is consistent with potential of mean force simulations of the dissociation pathway and with molecular dynamics simulations of biotin pullout, where Ser45 is seen to form a hydrogen bond with the ureido oxygen as biotin slips past this residue after breaking the native hydrogen bonds.


  • Organizational Affiliation

    Department of Bioengineering. University of Washington, Seattle 98195-2125, USA.


Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
PROTEIN (STREPTAVIDIN)
A, B
127Streptomyces avidiniiMutation(s): 1 
UniProt
Find proteins for P22629 (Streptomyces avidinii)
Explore P22629 
Go to UniProtKB:  P22629
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP22629
Sequence Annotations
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  • Reference Sequence
Small Molecules
Binding Affinity Annotations 
IDSourceBinding Affinity
BTN BindingDB:  1DF8 Kd: 0 (nM) from 1 assay(s)
ΔH: min: -1.23e+2, max: -6.69e+1 (kJ/mol) from 12 assay(s)
PDBBind:  1DF8 Kd: 0.2 (nM) from 1 assay(s)
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.51 Å
  • R-Value Free: 0.225 
  • R-Value Work: 0.169 
  • R-Value Observed: 0.162 
  • Space Group: I 2 2 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 46.2α = 90
b = 93.9β = 90
c = 104.6γ = 90
Software Package:
Software NamePurpose
X-PLORmodel building
SHELXL-97refinement
DENZOdata reduction
SCALEPACKdata scaling
X-PLORphasing

Structure Validation

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Ligand Structure Quality Assessment 


Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2000-09-20
    Type: Initial release
  • Version 1.1: 2008-04-27
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Derived calculations, Version format compliance
  • Version 1.3: 2021-11-03
    Changes: Database references, Derived calculations
  • Version 1.4: 2023-08-09
    Changes: Data collection, Refinement description