The mechanosensitive ion channel is related to channels found in a variety of other organisms
From:
Scripps Research Institute
February 17, 2022 -- Scientists at
Scripps Research have revealed the three-dimensional structure of Flycatcher1,
an aptly named protein channel that may enable Venus fly trap plants to snap
shut in response to prey. The structure of Flycatcher1, published February 14
in Nature Communications, helps shed light on longstanding
questions about the remarkably sensitive touch response of Venus fly traps. The
structure also gives the researchers a better understanding of how similar
proteins in organisms including plants and bacteria, as well as proteins in the
human body with similar functions (called mechanosensitive ion channels), might
operate.
"Despite how different Venus fly
traps are from humans, studying the structure and function of these
mechanosensitive channels gives us a broader framework for understanding the
ways that cells and organisms respond to touch and pressure," says
co-senior author and Scripps Research professor Andrew Ward, PhD.
"Every new mechanosensitive channel
that we study helps us make progress in understanding how these proteins can
sense force and translate that to action and ultimately reveal more about human
biology and health," adds co-senior author Ardem Patapoutian, PhD, a
Scripps Research professor who won the Nobel Prize in Physiology or Medicine
for research on the mechanosensitive channels that allow the body to sense touch
and temperature.
Mechanosensitive ion channels are like
tunnels that span the membranes of cells. When jostled by movement, the
channels open, letting charged molecules rush across. In response, cells then
alter their behavior -- a neuron might signal its neighbor, for instance. The
ability for cells to sense pressure and movement is important for people's
senses of touch and hearing, but also for many internal body processes -- from
the ability of the bladder to sense that it's full to the ability of lungs to
sense how much air is being breathed.
Previously, scientists had homed in on
three ion channels in Venus fly traps thought to be related to the ability of
the carnivorous plant to snap its leaves shut when its sensitive trigger hairs
get touched. One, Flycatcher1, caught researchers' attention because its
genetic sequence looked similar to a family of mechanosensitive channels, MscS,
found in bacteria.
"The fact that variants of this
channel are found throughout evolution tells us that it must have some fundamental,
important functions that have been maintained in different types of
organisms," says co-first author Sebastian Jojoa-Cruz, a graduate student
at Scripps Research.
In the new study, the researchers used
cryo-electron microscopy -- a cutting-edge technique that reveals the locations
of atoms within a frozen protein sample -- to analyze the precise arrangement
of molecules that form the Flycatcher1 protein channel in Venus fly trap
plants. They found that Flycatcher1 is, in many ways, similar to bacterial MscS
proteins -- seven groups of identical helices surrounding a central channel.
But, unlike other MscS channels, Flycatcher1 has an unusual linker region
extending outward from each group of helices. Like a switch, each linker can be
flipped up or down. When the team determined the structure of Flycatcher1, they
found six linkers in the down position, and just one flipped up.
"The architecture of Flycatcher1's
channel core was similar to other channels that have been studied for years,
but these linker regions were surprising," says Kei Saotome, PhD, a former
postdoctoral research associate at Scripps Research and co-first author of the
new paper.
To help elucidate the function of these
switches, the researchers altered the linker to disrupt the up position.
Flycatcher1, they found, no longer functioned as usual in response to pressure;
the channel remained open for a longer duration when it would normally close
upon removal of pressure.
"The profound effect of this
mutation tells us that the conformations of these seven linkers is likely
relevant for how the channel works," says co-senior author Swetha Murthy,
PhD, of Vollum Institute at Oregon Health and Science University, a former postdoctoral
research associate at Scripps Research.
Now that they solved the molecular
structure, the research team is planning future studies on the function of
Flycatcher1 to understand how different conformations affect its function. More
work is also needed to determine whether Flycatcher1 is solely responsible for
the snapping shut of Venus fly trap leaves, or whether other suspected channels
play complementary roles.
In addition
to Jojoa-Cruz, Saotome, Murthy, Patapoutian and Ward, authors of the study, "Structural
insights into the Venus flytrap mechanosensitive ion channel Flycatcher1,"
are Che Chun Alex Tsui and Wen-Hsin Lee of Scripps Research, and Mark Sansom of
University of Oxford.
https://www.sciencedaily.com/releases/2022/02/220217141334.htm
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