The Protein/RNA World and the Origin of Life (original) (raw)
Related papers
2020
The emergence of proteins in the prebiotic world was a watershed event at the origin of life. With their astonishing versatility, the protein enzymes catalyzed crucial biochemical reactions within protocells into more complex biomolecules in diverse metabolic pathways, whereas structural proteins provided strength and permeability in the cell membrane. Five major biochemical innovations followed in succession after availability of various kinds of protein molecules during decoding and translation of mRNAs. These are: (1) the modification of the phospholipid membrane into the plasma membrane; (2) the origin of primitive cytoplasm; (3) primitive gene regulation; (4) the beginnings of the virus world; and (5) the advent of DNA. The creative role of viruses during prebiotic synthesis led to the origin of the DNA world, when DNA replaced mRNA as the major genome of the protocells. With the advent of DNA, replication of information was entirely dissociated from its expression. Because DNA...
The origins of life: novel perspectives over an old problem
Bulletin of Regional Natural History (BORNH), 2021
Life probably appeared on Earth around 4 billion years ago and was globally diffused within the next 500 million years. It is debated whether life emerged in a superficial terrestrial environment, as generally maintained by "primordial-soup" models, or in association with submarine hydrothermal vents. Simulation experiments show that abiotic formation of simple organic molecules from CO 2 and H 2 , and of peptides from free amino acids is thermodynamically favoured under hydrothermal-vent conditions. In contrast, proposed pathways of abiotic synthesis of nucleotides and RNA fit better with superficial scenarios subject to wet/dry cycles. The "RNA World" hypothesis posits that a critical step towards life was the appearance of RNA enzymes (ribozymes) that catalysed RNA replication and random α-amino acid polymerization. The narrative presented here suggests that ribozyme interaction with peptides underpinned the emergence of populations of "protoribosomes" and virus-like RNA "protochromosomes" depending on each other for replication and subject to Darwinian evolution. The establishment of a genetic code coupled RNA and peptide evolution. RNA chaperoning of peptides positively selected self-folding peptide sequences, thus paving the way to the evolution of biologically active protein architectures. Association of informationally interlinked protoribosomes BORNH Review Article 12
Functional capabilities of the earliest peptides and the emergence of life
Genes, 2011
Considering how biological macromolecules first evolved, probably within a marine environment, it seems likely the very earliest peptides were not encoded by nucleic acids, or at least not via the genetic code as we know it. An objective of the present work is to demonstrate that sequence-independent peptides, or peptides with variable and unreliable lengths and sequences, have the potential to perform a variety of chemically useful functions such as anion and cation binding and membrane and channel formation as well as simple types of catalysis. These functions tend to be performed with the assistance of the main chain CONH atoms rather than the more variable or limited side chain atoms of the peptides presumed to exist then.
Origins of Life: Chemistry and Evolution
Progress in understanding the origins of life will be enhanced if models and their predictions are clearly understood and explicitly articulated. Two distinct models can be used to explain the genesis of biopolymers during the origins of life. In one model, which has been pursued for nearly 50 years, RNA is the result of inherent chemical reactivities of prebiotic chemical species. RNA invented evolution. This model enables the prediction that if the conditions of the ancient earth are sufficiently constrained, chemists will discover the direct synthetic pathways that produced RNA. In a fundamentally different model, which is more recent, RNA and other biopolymers are proposed to be the result of prolonged, creative, selection-based changes that occurred during chemical evolution and overlap with early biological evolution. Evolution invented RNA. In this evolutionary model, inherent chemical reactivities are not necessarily relevant to the origins of life and do not predict biosynt...
Information is the currency of life, but the origin of prebiotic information remains a mystery. We propose transitional pathways from the cosmic building blocks of life to the complex prebiotic organic chemistry that led to the origin of information systems. The prebiotic information system, specifically the genetic code, is segregated, linear, and digital and probably appeared during biogenesis four billion years ago. In the peptide/RNA world, lipid membranes randomly encapsulated amino acids, RNA, and protein molecules, drawn from the prebiotic soup, to initiate a molecular symbiosis inside the protocells. This endosymbiosis led to the hierarchical emergence of several requisite components of the translation machine: tRNAs, aaRS, mRNAs, and ribosomes. When assembled in the right order, the translation machine created biosynthetic polypeptides, a process that transferred information from mRNAs to proteins. This was the beginning of the prebiotic information age. The molecular attra...