posted on 2021-01-15, 23:03authored byAkarawin Hongdusit, Jerome M. Fox
Allosteric regulation enables dynamic
adjustments to protein function
that permit tight control over cellular biochemistry. Discrepancies
in the allosteric systems of related proteins can thus reveal important
differences in their susceptibilities to influential stimuli (e.g.,
allosteric ligands, mutations, or post-translational modifications).
This study uses an optogenetic actuator as a tool to compare the allosteric
systems of two structurally related regulatory proteins: protein tyrosine
phosphatase 1B (PTP1B) and T-cell protein tyrosine phosphatase (TCPTP).
It begins with an interesting observation: The fusion of a protein
light switch to the allosterically influential α7 helix of PTP1B
permits optical modulation of its catalytic activity, but a similar
fusion to TCPTP does not. A subsequent analysis of different PTP chimeras
shows that replacing regions of TCPTP with homologous regions from
PTP1B can enhance photocontrol; as TCPTP becomes more “PTP1B-like”,
its photosensitivity increases. Interestingly, the structural changes
required for photocontrol also enhance the sensitivity of TCPTP to
other allosteric inputs, notably, an allosteric inhibitor and a newly
reported activating mutation. Our findings indicate that the allosteric
functionality of the α7 helix of PTP1B is not conserved across
the PTP family and highlight residues necessary to transfer this functionality
to other PTPs. More broadly, our results suggest that simple gene
fusion events can strengthen allosteric communication within individual
protein domains and describe an intriguing application for optogenetic
actuators as structural probesa sort of physically disruptive
“ratchet”for studying protein allostery.