(AGENPARL) – mar 14 novembre 2023 Source: Tokyo Institute of Technology
For immediate release: November 14, 2023
Headline: Engineering Bacteria to Biosynthesize Intricate Protein Complexes
(Tokyo, November 14) Protein cages found in nature within microbes help
weather its contents from the harsh intracellular environment—an
observation with many bioengineering applications. Tokyo Tech researchers
recently developed an innovative bioengineering approach using genetically
modified bacteria; these bacteria can incorporate protein cages around
protein crystals. This in-cell biosynthesis method efficiently produces
highly customized protein complexes, which could find applications as
advanced solid catalysts and functionalized nanomaterials.
In nature, proteins can assemble to form organized complexes with myriad
shapes and purposes. Thanks to the remarkable progress in bioengineering
over the past few decades, scientists can now produce customized protein
assemblies for specialized applications. For example, protein cages can
confine enzymes that act as catalysts for a target chemical reaction,
weathering it from a potentially harsh cell environment. Similarly, protein
crystals—structures composed of repeating units of proteins—can serve as
scaffolds for synthesizing solid materials with exposed functional
terminals.
However, incorporating (or ‘encapsulating’) foreign proteins on the surface
of a protein crystal is challenging. Thus, synthesizing protein crystals
encapsulating foreign protein assemblies has been elusive. So far, no
efficient methods exist to achieve this goal, and the types of protein
crystals produced are limited. But what if bacterial cellular machinery can
achieve this goal?
In a recent study, a research team from Tokyo Institute of Technology,
including Professor Takafumi Ueno, reported a new *in-cell* method for
encapsulating protein cages with diverse functions on protein crystals.
Their paper, published in *Nano Letters,* represents a substantial
breakthrough in protein crystal engineering.
The team’s innovative strategy involves genetically modifying *Escherichia
coli* bacteria to produce two main building blocks: polyhedrin monomer
(PhM) and modified ferritin (Fr). On the one hand, PhMs naturally combine
within cells to form a well-studied protein crystal called polyhedra
crystal (PhC). On the other hand, 24 Fr units are known to combine to form
a stable protein cage. *“*Ferritin has been widely used as a template for
constructing bio-nano materials by modifying its internal and external
surfaces. Thus, if the formation of a Fr cage and its subsequent
immobilization onto PhC can be performed simultaneously in a single cell,
the applications of in-cell protein crystals as bio-hybrid materials will
be expanded,” explains Prof. Ueno.
To immobilize the Fr cages into PhC, the researchers modified the gene
coding for Fr to include an a-helix(H1) tag of PhM, thus creating H1-Fr.
The reasoning behind this approach is that the H1-helixes naturally present
in PhM molecules interact significantly with the tags on H1-Fr, acting as
‘recruiting agents’ that bind the foreign proteins onto the crystal.
Using advanced microscopy, analytical, and chemical techniques, the
research team verified the validity of their proposed approach. Through
various experiments, they found that the resulting crystals had a
core–shell structure, namely a cubic PhC core about 400 nanometers wide
covered in five or six layers of H1-Fr cages.
This strategy for the biosynthesis of functional protein crystals holds
much promise for applications in medicine, catalysis, and biomaterials
engineering. “H1-Fr cages have the potential to immobilize external
molecules inside them for molecular delivery,” remarks Prof. Ueno, “Our
results indicate that the H1-Fr/PhC core–shell structures, displaying H1-Fr
cages on the outer surface of the PhC core, can be individually controlled
at the nanoscale level. By accumulating different functional molecules in
the PhC core and H1-Fr cage, hierarchical nanoscale-controlled crystals can
be constructed for advanced biotechnological applications.”
Future works in this field will help us realize the true potential of
bioengineering protein crystals and assemblies. With any luck, these
efforts will pave the way to a healthier and more sustainable future.
*Reference*
Authors:
Thuc Toan Pham1, Satoshi Abe1,*, Koki Date1, Kunio Hirata2, Taiga Suzuki1,
and Takafumi Ueno1,3,*
Title:
Displaying a protein cage on a protein crystal by in-cell crystal
engineering
Journal:
*Nano Letters*
DOI:
https://doi.org/10.1021/acs.nanolett.3c02117
Affiliations:
1School of Life Science and Technology, Tokyo Institute of Technology
2SR Life Science Instrumentation Unit, RIKEN/SPring-8 Center
3Living Systems Materialogy (LiSM) Research Group, International Research
Frontiers Initiative (IRFI), Tokyo Institute of Technology
Figure: https://tokyotech.box.com/s/fyud4l3ufsp400zbf09md7w813uk5wpb
(Please download from the above URL)
Figure title: Figure 1. In-cell assembly process of H1-Fr/PhC
Figure captions: This diagram shows how H1-Fr monomers and polyhedrin
monomers (PhMs) combine to spontaneously form a complex core–shell
structure inside the *E. coli* bacteria
Contact
Emiko Kawaguchi
Tokyo Institute of Technology
*About Tokyo Institute of Technology *
Tokyo Tech stands at the forefront of research and higher education as the
leading university for science and technology in Japan. Tokyo Tech
researchers excel in fields ranging from materials science to biology,
computer science, and physics. Founded in 1881, Tokyo Tech hosts over
10,000 undergraduate and graduate students per year, who develop into
scientific leaders and some of the most sought-after engineers in industry.
Embodying the Japanese philosophy of “monotsukuri,” meaning “technical
ingenuity and innovation,” the Tokyo Tech community strives to contribute
to society through high-impact research.
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