Tiny protein motor fuels bacterial movement

Date:
September 15, 2020
Source:
University of Copenhagen The Faculty of Health and Medical Sciences
Summary:
The ability to move is key for bacteria like some strains of
salmonella and E. coli to efficiently spread infections. They
can propel themselves forward using threads, known as flagella,
powered by the flagellar rotary motor. But how this rotary motor
is powered has been a mystery among scientists. Now, researchers
show that the bacterial flagellar motor is powered by yet another
even tinier, rotary motor.



FULL STORY ========================================================================== There are billions of bacteria around us and in our bodies, most of
which are harmless or even helpful. But some bacteria such as E. coli and salmonella can cause infections. The ability to swim can help bacteria to
seek out nutrients or to colonize parts of the body and cause infection.


========================================================================== Researchers from the Faculty of Health and Medical Sciences, University of Copenhagen, have now provided fundamental insight into how this bacterial movement is powered, solving a yearlong mystery within the field.

'A lot of bacteria can move, or swim, because they have long threads, also known as flagella, which they can use to propel themselves forward. They
do this by rotating these threads. The rotation is powered by a rotary
motor, which again is powered by a protein complex known as the stator
unit. This is all well known within our field. What we now show is how
this stator unit powers the motor, which has been a mystery so far',
says Associate Professor and Group Leader Nicholas Taylor, Novo Nordisk Foundation Center for Protein Research.

Quite surprisingly, the team shows that the stator unit itself is in
fact also a tiny rotary motor. This tiny motor powers the large motor,
which makes the threads rotate, causing the bacteria to move. The results contradict existing theories on the mechanism of the stator unit, and
this new knowledge might be useful in the fight against bacteria-based diseases.

'Most researchers, including ourselves, actually thought that the
technical mechanism and the architecture of the stator unit was quite
different to what our study shows. Knowing the actual composition and
function of this unit paves the way for therapeutic purposes. When we
know what makes bacteria move, we might also be able to inhibit this
movement and thereby stop it from spreading', says Nicholas Taylor.

Cryo-electron microscopy reveals the architecture of the motor The
researchers determined the structure of the stator unit complex by using cryo-electron microscopy. Working with this technique, they were able
to elucidate its architecture, see how it is activated and provide a
detailed model for how it powers rotation of the flagellar motor.

"The motor consists of two proteins: MotA and MotB. The MotB protein is anchored to the cell wall, and is surrounded by MotA proteins, which,
upon dispersion of the ion motive force, rotates around MotB. The
rotation of MotA in turn powers rotation of the large bacteria motor,"
says Nicholas Taylor.

"Furthermore, our model shows how the stator unit can power rotation of
the bacterial flagellar motor in both directions, which is crucial for
the bacteria to change their swimming direction. Without direction change, bacteria would only be able to swim straight in one direction." Next step
for the group is to find out if it is possible to inhibit the stator
units using chemical compounds, which could have antibiotic effects.


========================================================================== Story Source: Materials provided
by University_of_Copenhagen_The_Faculty_of_Health_and
Medical_Sciences. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Mo`nica Santiveri, Aritz Roa-Eguiara, Caroline Ku"hne, Navish
Wadhwa,
Haidai Hu, Howard C. Berg, Marc Erhardt, Nicholas
M.I. Taylor. Structure and Function of Stator Units of the Bacterial
Flagellar Motor. Cell, 2020; DOI: 10.1016/j.cell.2020.08.016 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200915105959.htm

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