bi7b00657_si_001.pdf (1.81 MB)
Periplasmic Binding Protein Dimer Has a Second Allosteric Event Tied to Ligand Binding
journal contribution
posted on 2017-09-06, 00:00 authored by Le Li, Sudipa Ghimire-Rijal, Sarah L. Lucas, Christopher B. Stanley, Edward Wright, Pratul K. Agarwal, Dean A. Myles, Matthew J. CuneoThe
ligand-induced
conformational changes of periplasmic binding
proteins (PBP) play a key role in the acquisition of metabolites in
ATP binding cassette (ABC) transport systems. This conformational
change allows for differential recognition of the ligand occupancy
of the PBP by the ABC transporter. This minimizes futile ATP hydrolysis
in the transporter, a phenomenon in which ATP hydrolysis is not coupled
to metabolite transport. In many systems, the PBP conformational change
is insufficient at eliminating futile ATP hydrolysis. Here we identify
an additional state of the PBP that is also allosterically regulated
by the ligand. Ligand binding to the homodimeric apo PBP leads to
a tightening of the interface α-helices so that the hydrogen
bonding pattern shifts to that of a 310 helix, in-turn
altering the contacts and the dynamics of the protein interface so
that the monomer exists in the presence of ligand.