Cooperative Allostery and Structural Dynamics of Streptavidin at Cryogenic- and Ambient-temperature

Abstract

Multimeric protein assemblies are abundant in nature. Streptavidin is an attractive protein that provides a paradigm system to investigate the intra- and intermolecular interactions of multimeric protein complexes. Also, it offers a versatile tool for biotechnological applications. Here, we present two apo-streptavidin structures, the first one is an ambient temperature Serial Femtosecond X-ray crystal (Apo-SFX) structure at 1.7 Å resolution and the second one is a cryogenic crystal structure (Apo-Cryo) at 1.1 Å resolution. These structures are mostly in agreement with previous structural data. Combined with computational analysis, these structures provide invaluable information about structural dynamics of apo streptavidin. Collectively, these data further reveal a novel cooperative allostery of streptavidin which binds to substrate via water molecules that provide a polar interaction network and mimics the substrate biotin which displays one of the strongest affinities found in nature.

Biotin’s Lessons in Drug Design

“…23 Very recently, a fully solvated, ambient temperature apo structure of streptavidin with seven waters in the biotin binding pocket (Figure 2E) using serial femtosecond X-ray 24 crystallography was solved to a resolution of 1.7 Å. 25 All five calculated ice-like ring waters would be displaced by biotin's two five-membered rings (Figure 2D), while the three waters observed crystallographically would be displayed by the ureido ring alone (Figure 2F). The remaining four crystallographic waters are situated in the hydrophobic portion of the binding pocket that overlays with the valeric acid side chain of biotin when bound (Figure 2F).…”