23.9 Synthetic Cell Building Block Supply

Synthetic Cell Building Block Supply refers to the provision of the finished, ready-to-use monomeric units, such as amino acids, nucleotides, activated sugars, and lipid precursors, that a synthetic cell's polymerization and assembly machinery directly incorporates into proteins, nucleic acids, and membranes, representing the final stage of preparation before these units are consumed in macromolecular synthesis.

Amino Acid Supply

Amino Acid Biosynthetic Supply

The synthetic cell must provide a supply of amino acids, either through internal biosynthesis from precursor intermediates or through external provision, in order to sustain ongoing protein synthesis.

Essential Amino Acid External Dependency and Nonessential Amino Acid Formation

Certain amino acids, referred to as essential in this context, cannot be synthesized internally and must instead be supplied externally, while nonessential amino acids can be formed directly within the synthetic cell from available precursors.

Nucleotide Supply

Nucleotide Precursor Biosynthesis

Nucleotide precursors are synthesized through dedicated biosynthetic pathways that assemble the nitrogenous base, sugar, and phosphate components characteristic of nucleotide structure.

Purine, Pyrimidine, Ribonucleotide, and Deoxyribonucleotide Supply

Purine and pyrimidine precursor supply provide the two distinct classes of nitrogenous base required for nucleotide synthesis, while ribonucleotide supply provides the building blocks needed for RNA and deoxyribonucleotide supply provides the corresponding building blocks needed for DNA.

Lipid and Sugar-Related Supply

Activated Sugar Building Block Supply

Activated sugar building blocks, chemically primed for incorporation into larger carbohydrate or glycosylated structures, must be supplied to support any synthesis pathway that depends on adding sugar units to a growing product.

Fatty Acid and Isoprenoid Precursor Supply

Fatty acid precursors supply the building blocks needed for membrane lipid synthesis, while isoprenoid precursors supply an alternative class of lipid-related building block used in certain membrane components and other cellular structures.

Supply for Cofactors and Groups

Cofactor and Prosthetic Group Precursor Supply

Cofactor precursor supply provides the building blocks needed to construct the small molecules that support enzyme function, while prosthetic group precursor supply provides the building blocks for more tightly bound functional groups permanently associated with specific proteins.

Supply Matched to Consuming Processes

Protein, RNA, DNA, and Membrane Synthesis Building Block Availability

Building block availability must be matched to each specific consuming process, with amino acids available in sufficient quantity to support protein synthesis, nucleotides available to support RNA and DNA synthesis, and lipid-related precursors available to support membrane synthesis, each representing a distinct downstream demand on the overall building block supply system.

Balancing the Whole System

Building Block Pool Balance and Supply Prioritization

Maintaining balance among all building block pools requires that no single class of precursor be allowed to dominate resource allocation at the expense of others, and supply prioritization establishes which building blocks receive preferential provision when overall supply capacity is insufficient to meet total demand.

Overall Reliance

Synthetic Cell Biosynthetic Dependency

The overall reliance of a synthetic cell on internally synthesized versus externally supplied building blocks defines its biosynthetic dependency, a property with direct consequences for how self-sufficient the cell can be within a given operating environment.

Summary

Synthetic Cell Building Block Supply encompasses the provision of amino acids, nucleotide precursors, activated sugars, fatty acids, isoprenoids, and cofactor and prosthetic group precursors needed for protein, nucleic acid, and membrane synthesis. Balancing these pools and prioritizing supply under limited capacity determines the synthetic cell's overall biosynthetic dependency and its capacity to sustain ongoing macromolecular production.