Abstract
Recent developments in Origins of Life research have focused on substantiating the narrative of an abiotic emergence of nucleic acids from organic molecules of low molecular weight, a paradigm that typically sidelines the roles of peptides. Nevertheless, the simple synthesis of amino acids, the facile nature of their activation and condensation, their ability to recognize metals and cofactors and their remarkable capacity to self-assemble make peptides (and their analogues) favourable candidates for one of the earliest functional polymers. In this mini-review, we explore the ramifications of this hypothesis. Diverse lines of research in molecular biology, bioinformatics, geochemistry, biophysics and astrobiology provide clues about the progression and early evolution of proteins, and lend credence to the idea that early peptides served many central prebiotic roles before they were encodable by a polynucleotide template, in a putative ‘peptide-polynucleotide stage’. For example, early peptides and mini-proteins could have served as catalysts, compartments and structural hubs. In sum, we shed light on the role of early peptides and small proteins before and during the nucleotide world, in which nascent life fully grasped the potential of primordial proteins, and which has left an imprint on the idiosyncratic properties of extant proteins.
Highlights
Proteins are the macromolecules responsible for performing the vast majority of biological functions in extant life, and yet their importance during the Origin of Life is often underappreciated or even neglected
Named by the Swedish biochemist Jöns Jacob Berzelius after the ancient Greek word πρώτειος, proteins were most likely the earliest biopolymer. The evidence for this comes from many lines of research, including: (i) the ease with which amino acid building blocks can emerge spontaneously through simple and unsupervised gas-phase chemistry [9,10]; (ii) the prevalence of some canonical amino acids in carbonaceous meteorites [11,12]; and (iii) the facile nature of the condensation reaction between amino acids [13] which can be mediated by wet–dry cycles in ‘warm little pond’ terrestrial settings, or under highpressure high-temperature conditions in hydrothermal vents [14,15,16], and may even be possible in the interstellar medium as well [17]
Because of the large size and complexity of modern DNA polymerases and ribonucleotide reductases compared to many other types of proteins, we imagine this at the final stage in our protein–nucleic acid coevolution scheme prior to LUCA, as it 5 presupposes a translational machinery capable of synthesizing large multi-domain proteins
Summary
Proteins are the macromolecules responsible for performing the vast majority of biological functions in extant life, and yet their importance during the Origin of Life is often underappreciated or even neglected. Named by the Swedish biochemist Jöns Jacob Berzelius after the ancient Greek word πρώτειος (meaning ‘first’), proteins were most likely the earliest biopolymer The evidence for this comes from many lines of research, including: (i) the ease with which amino acid building blocks can emerge spontaneously through simple and unsupervised gas-phase chemistry [9,10]; (ii) the prevalence of some canonical amino acids (cAAs) in carbonaceous meteorites [11,12]; and (iii) the facile nature of the condensation reaction between amino acids [13] which can be mediated by wet–dry cycles in ‘warm little pond’ terrestrial settings, or under highpressure high-temperature conditions in hydrothermal vents [14,15,16], and may even be possible in the interstellar medium as well [17]. This scenario provides an alternative to a purely ‘organic chemical’ emergence of polynucleotides and invites a new way of thinking about the origins of life that combines the ‘best’ of what peptides and nucleotides had to offer at distinct stages of emergence (figure 1)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
