1MEP

Crystal Structure of Streptavidin Double Mutant S45A/D128A with Biotin: Cooperative Hydrogen-Bond Interactions in the Streptavidin-Biotin System.

Summary for 1MEP

• Entry DOI: 10.2210/pdb1mep/pdb
• Related: 1MK5 1SWE
• Descriptor: Streptavidin, BIOTIN (3 entities in total)
• Functional Keywords: homotetramer, biotin-binding protein
• Biological source: Streptomyces avidinii
• Cellular location: Secreted: P22629
• Total number of polymer chains: 4
• Total formula weight: 53862.55

Authors

Hyre, D.E.,Le Trong, I.,Merritt, E.A.,Stenkamp, R.E.,Green, N.M.,Stayton, P.S. (deposition date: 2002-08-08, release date: 2003-09-02, Last modification date: 2024-02-14)

Primary citation

Hyre, D.E.,Le Trong, I.,Merritt, E.A.,Eccleston, J.F.,Green, N.M.,Stenkamp, R.E.,Stayton, P.S.
Cooperative hydrogen bond interactions in the streptavidin-biotin system
Protein Sci., 15:459-467, 2006

PubMed Abstract: The thermodynamic and structural cooperativity between the Ser45- and D128-biotin hydrogen bonds was measured by calorimetric and X-ray crystallographic studies of the S45A/D128A double mutant of streptavidin. The double mutant exhibits a binding affinity approximately 2x10(7) times lower than that of wild-type streptavidin at 25 degrees C. The corresponding reduction in binding free energy (DeltaDeltaG) of 10.1 kcal/mol was nearly completely due to binding enthalpy losses at this temperature. The loss of binding affinity is 11-fold greater than that predicted by a linear combination of the single-mutant energetic perturbations (8.7 kcal/mol), indicating that these two mutations interact cooperatively. Crystallographic characterization of the double mutant and comparison with the two single mutant structures suggest that structural rearrangements at the S45 position, when the D128 carboxylate is removed, mask the true energetic contribution of the D128-biotin interaction. Taken together, the thermodynamic and structural analyses support the conclusion that the wild-type hydrogen bond between D128-OD and biotin-N2 is thermodynamically stronger than that between S45-OG and biotin-N1.

PubMed: 16452627
DOI: 10.1110/ps.051970306

Experimental method

X-RAY DIFFRACTION (1.65 Å)