Allosteric Regulation of Molecular Tunnels

Enzymes that harbor transient tunnels have a complex interplay of allostery that links their assembly/disassembly with the catalytic cycle. A question that remains elusive is- are tunnels passive transport conduits or participate in active passage? To decipher this, we unravel the precise orchestration of signal transduction, associated conformational changes and their link with formation of the transient ammonia tunnel by studying PurL, a key bi-functional ammonia channeling enzyme, involved in purine biosynthesis. We show ammonia passage in PurL is controlled by  multiple allosteric signals that leads to a transient tunnel that fluctuates gives rise to a breathing channel that likely acts as selectivity filter, occluding solvent and providing directionality for ammonia passage. Comparison  reveals that this relay is observed in several systems, asserting a common generic mechanism[1]

References:

1) Sharma et. al. Science Advances, (2020) Vol. 6, no. 14, eaay7919