Artificial Organelle for Energy Production in Artificial Cell
Yutetsu Kuruma1, Toshiharu Suzuki2, Masasuke Yoshida3, Takuya Ueda1
1
Department of Medical Genome Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Japan
2
ATP Synthesis Regulation Project, ICORP, Japan Science and Technology Corporation, Japan
3
Department of Molecular Biosciences, Kyoto Sangyo University, Japan
kuruma@molbio.t.u-tokyo.ac.jp
Abstract
built up through an internal metabolic process such as gene
expression. If both bR and FoF1 proteins were synthesized
in the presence of organelle-sized vesicles, it would be
possible to construct in vitro the bR-FoF1 liposomes as a
consequence of the artificial protein synthesis and the
self-organization of the synthesized proteins. Additionally,
so produced bR-FoF1 liposomes can be applied as a
bioenergy-producible plant that activates further biological
reaction. For instance, if the produced ATP could be used
for protein synthesis reaction, the whole system would
represent an energetically independent autonomous system.
In the ECAL11 meeting, we present some experimental
achievements toward the construction of bR-FoF1 liposome
(2, 3). Our recent results show that bR was synthesized in a
cell-free protein synthesis system (4) in the presence of
liposomes and all-trans retinal. Fo complex, the membrane
integrated part of FoF1, was synthesized in situ and formed
the desired FoF1 complex in combination with a supplied
F1. FoF1 complex was fully functional, by showing ATPase
driven H+-translocation activity. These results imply that the
bottom up construction of an artificial organelle, which is
capable of generating the bioenergy, is experimentally
feasible. We believe that our bR-FoF1 liposomes will be
essential machinery for constructing artificial cells.
Autonomous production of biological energy is one of
the primal processes in living cells. In cells, the
bio-energy presents as adenosine or guanosine
triphosphate (ATP or GTP) is used for the most of
cellular reactions. ATP is produced through the
glycolytic cycle by a series of dedicated enzymes in
cytosol, or through the oxidative phosphorylation of
adenosine diphosphate (ADP), operated by ATP
synthase, which is located on lipid membrane. For
instance, in mitochondria, the proton potential across the
membrane, generated by an electron transport chain, is
eventually dissolved through FoF1-ATP synthase
(FoF1). The flux of protons drives FoF1 and activates
the synthesis of ATP, from ADP and Pi. On the other
hand, bacteriorhodopsin (bR) is widely known as proton
pump machinery that transports the protons to the other
side of membrane due to light stimulation. Therefore,
our idea is that if the bR and FoF1 were synthesized on a
liposome membrane, the resulting liposome is able to
generate ATP (see Figure 1).
References
1.
2.
3.
4.
Figure 1. Schematic of bR-FoF1 liposome. Light induced
bacteriorhodopsin pumps H+ into liposome and produced H+
gradient is used for FoF1-ATP synthase to synthesize ATP.
Racker and Stoeckenius (1) have studied a model system by
combing purple membrane, which contains bR, and isolated
ATP synthase in phospholipid vesicles. In order to design
and construct a synthetic cell in the synthetic biology
context, this kind of “bioreactor” should be autonomously
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