posted on 2022-01-19, 15:36authored byXu Dong, Ling-Yun Qin, Zhou Gong, Sanbo Qin, Huan-Xiang Zhou, Chun Tang
Nonspecific
binding of crowder proteins with functional proteins
is likely prevalent in vivo, yet direct quantitative
evidence, let alone residue-specific information, is scarce. Here
we present nuclear magnetic resonance (NMR) characterization showing
that bovine serum albumin weakly but preferentially interacts with
the histidine carrier protein (HPr). Notably, the binding interface
overlaps with that for HPr’s specific partner protein, EIN,
leading to competition. The crowder protein thus decreases the EIN-HPr
binding affinity and accelerates the dissociation of the native complex.
In contrast, Ficoll-70 stabilizes the native complex and slows its
dissociation, as one would expect from excluded-volume and microviscosity
effects. Our atomistic modeling of macromolecular crowding rationalizes
the experimental data and provides quantitative insights into the
energetics of protein–crowder interactions. The integrated
NMR and modeling study yields benchmarks for the effects of crowded
cellular environments on protein–protein specific interactions,
with implications for evolution regarding how nonspecific binding
can be minimized or exploited.