Cell-Free Protein Synthesis System for Building Synthetic Cells

Summary

This protocol describes the Cell-Free Protein Synthesis (CFPS) system used in constructing synthetic cells. It outlines key stages with representative results in different micro-compartments. The protocol aims to establish best practices for diverse laboratories in the synthetic cell community, advancing progress in synthetic cell development.

Abstract

The Cell-Free Protein Synthesis (CFPS) system has been widely employed to facilitate the bottom-up assembly of synthetic cells. It serves as the host for the core machinery of the Central Dogma, standing as an optimal chassis for the integration and assembly of diverse artificial cellular mimicry systems. Despite its frequent use in the fabrication of synthetic cells, establishing a tailored and robust CFPS system for a specific application remains a nontrivial challenge. In this methods paper, we present a comprehensive protocol for the CFPS system, routinely employed in constructing synthetic cells. This protocol encompasses key stages in the preparation of the CFPS system, including the cell extract, template preparation, and routine expression optimization utilizing a fluorescent reporter protein. Additionally, we show representative results by encapsulating the CFPS system within various micro-compartments, such as monolayer droplets, double-emulsion vesicles, and chambers situated atop supported lipid bilayers. Finally, we elucidate the critical steps and conditions necessary for the successful assembly of these CFPS systems in distinct environments. We expect that our approach will facilitate the establishment of good working practices among various laboratories within the continuously expanding synthetic cell community, thereby accelerating progress in the field of synthetic cell development.

Introduction

The synthesis of synthetic or artificial cells has emerged as a highly prominent field of interdisciplinary research, attracting substantial interest from scientists across the domains of synthetic biology, chemistry, and biophysics. These scientists are united by the common goal of constructing a minimal living cell^1,2,3. The rapid growth of this field has been in step with significant advancements in critical technologies, such as recombinant DNA manipulation⁴, biomimetic materials⁵, and microfabrication techniques for compart....

Protocol

1. Extract preparation

1. Streak the E. coli BL21 (DE3) strain from a glycerol stock onto a Luria Bertani (LB) agar plate and incubate for at least 15 h at 37 °C.
2. Prepare an overnight preculture by inoculating a single colony from the freshly prepared LB plate into a 50 mL flask of Luria Bertani (LB) medium.
3. Inoculate 5 mL of preculture into 500 mL of 2xYTPG medium in a 3 L baffled Erlenmeyer flask. Grow it at 37 °C with vigorous shaking (between 220 rpm an.......

Discussion

This manuscript outlines a modified Cell-Free Protein Synthesis (CFPS) system designed for use in various micro-compartments across synthetic cell platforms, including water-in-oil droplets, GUVs, and SLBs. We utilized the standard E. coli recombinant protein expression host strain, BL21(DE3), as the source extract for constructing protein-centric synthetic cell systems. This approach yielded approximately 0.5 mg/mL of protein across different compartments. While other customized extract source strains could be .......

Materials

Name	Company	Catalog Number	Comments
1,2-dioleoyl-sn-glycero-3-phosphocholine(DOPC)	Avanti	850375P
1,2-dioleoyl-sn-glycero-3-phospho-L-serine (sodium salt)(DOPS)	Avanti	840035P
1,4 dithiothreitol (DTT)	Sigma-Aldrich	1.11474
1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)	Avanti	850457P
3,5-cyclic AMP (cAMP)	Sigma-Aldrich	A9501
50 mL tubes	Eppendorf	Eppendorf Tubes BioBased
50% hydrogen peroxide	Sigma-Aldrich	516813
Acetate	Sigma-Aldrich	A6283
Agar powder	Sigma-Aldrich	05040
Alanin	Sigma-Aldrich	A4349
Amicon Stirred Cells	MerckMillipore	UFSC05001
Ammonium acetate (NH4OAc)	Sigma-Aldrich	A7262
Arginin	Sigma-Aldrich	A4474
Asparagin	Sigma-Aldrich	A0884
Aspartat	Sigma-Aldrich	A5474
ATP	Roche	11140965001
Atto 488 DOPE	Sigma-Aldrich	67335
Atto 647N DOPE	Sigma-Aldrich	42247
Baffled Erlenmeyer flask	Shuniu	250 mL, 1000mL
Bovine Serum Albumin(BSA)	Roche	10711454001
Centrifugetube	Eppendorf	Eppendorf Tubes 3810X
Centrifugetube rack	Eppendorf	0030119819
Chemiluminescence and epifluorescence imaging system	Uvitec	Alliance Q9 Advanced
Chloroform	Sigma-Aldrich	288306
Confocal Laser Scanning Microscopy (LSM)	ZEISS	LSM 780
Countess Cell Counting Chamber Slides	Thermo Fisher Scientific	C10283
Coverslip	Thermo Scientific	Menzel BB02400500A113MNZ0
creatine kinase (CK)	Roche	10127566001
Creatine phosphate (CP)	Sigma-Aldrich	10621714001
Culture dish	Huanqiu	90 mm
Cystein	Sigma-Aldrich	C5360
Cytidine 5'-triphosphate disodium salt (CTP)	aladdin	C101487
Dialysis membrane	Spectrum	Standard RC Tubing MWCO: 12-14 kD
E.Z.N.A. Cycle Pure Kit	Omega Bio-Tek	D6492-01
Electro-Heating Standing-Temperature Cultivator	Yiheng instrument	DHP-9602
Ethylenediaminetetraacetic acid(EDTA)	Biosharp	1100027
Fluorescent plate reader	BioTek	Synergy 2
Fluorinated oil	Suzhou CChip scientific instrument	2%HFE7500
Folinic acid	Sigma-Aldrich	47612
French Press	G.Heinemann	HTU-DIGI-Press
Glucose	Sigma-Aldrich	G7021
Glutamat	Sigma-Aldrich	G5667
Glutamin	Sigma-Aldrich	G5792
Glycerol	Sigma-Aldrich	G5516
Glycin	Sigma-Aldrich	G7126
Guanosine 5'-triphosphate sodium salt hydrate(GTP)	Roche	10106399001
HEPES	Sigma-Aldrich	H3375
HiPrep Q FF 16/10	Cytiva	28936543
Histidin	Sigma-Aldrich	H6034
Isoleucin	Sigma-Aldrich	I5281
Isopropyl-β-D-thiogalactopyranoside (IPTG)	Sigma-Aldrich	I5502
K2HPO4	Sigma-Aldrich	P8281
KH2PO4	Sigma-Aldrich	P5655
Leucin	Sigma-Aldrich	L6914
Lysin	Sigma-Aldrich	L5501
Magnesium acetate tetrahydrate (Mg(OAc)2 )	Sigma-Aldrich	M5661
Magnesium chloride(MgCl2)	Sigma-Aldrich	M2670
Methionin	Sigma-Aldrich	M8439
Microcentrifuge	Eppendorf	5424 R
Mineral oil	Sigma-Aldrich	M5904
Mini-PROTEAN Tetra Cell Systems	Bio-Rad	1645050
Multipurpose Centrifuge	Eppendorf	5810 R
NaN3	Sigma-Aldrich	S2002
Nucleic Acid & Protein UV-Assay Measurements	IMPLEN	NanoPhotometer N60
NucleoBond Xtra Maxi kit for transfection-grade plasmid DNA	MACHEREY-NAGEL	740414.5
Nunc-Immuno MicroWell 96 well polystyrene plates	Sigma-Aldrich	P8616
PCR Thermal Cycler	Eppendorf	Mastercycler nexus
Peptone	Sigma-Aldrich	83059
Phenylalanin	Sigma-Aldrich	P8740
Phosphoenolpyruvat (PEP)	GLPBIO	GC44635
PMSF	Sigma-Aldrich	PMSF-RO
Polyethylene glycol 8000 (PEG 8000)	Sigma-Aldrich	89510
Potassium Acetate(KOAc)	Sigma-Aldrich	P5708
Potassium chloride(KCl)	Sigma-Aldrich	P9541
Potassium glutamate (K-glutamate)	Sigma-Aldrich	G1501
Potassium hydroxide(KOH)	Sigma-Aldrich	221473
Prolin	Sigma-Aldrich	P8865
Pyruvate kinase (PK)	Sigma-Aldrich	P9136
Serin	Sigma-Aldrich	S4311
Shaker	Zhichushakers	ZQZY-AF8
Sodium chloride(NaCl)	Sigma-Aldrich	S5886
Sodium hydroxide(NaOH)	Sigma-Aldrich	S5881
Sucrose	aladdin	S112226
Sulfuric acid	Sigma-Aldrich	339741
Syringe Filters	Jinteng	0.45 μm
Test tube	Shuniu	20 mL
TGX FastCast Acrylamide Kit, 12%	Bio-Rad	#1610175
ThermoMixer	Eppendorf	ThermoMixer C
Threonin	Sigma-Aldrich	T8441
Tris base	Sigma-Aldrich	V900483
tRNA	Roche	10109550001
Tryptone	Sigma-Aldrich	T7293
Tryptophan	Sigma-Aldrich	T8941
Tyrosin	Sigma-Aldrich	T8566
UTP Trisodium salt (UTP)	aladdin	U100365
Vacuum Pump with Circulated Water System	Zhengzhou Greatwall Scientific Industrial and Trade Co.Ltd	SHB-
Valin	Sigma-Aldrich	V4638
Vortex Mixers	Kylin-Bell	Vortex QL-861
Water purification system	MerckMillipore	Direct ultrapure water (Type 1)
Yeast extract	Sigma-Aldrich	70161
β-mercaptoethanol	Sigma-Aldrich	444203