A search for relict ribonucleotide and amino acid sequences that played a key role in the development of the ribosome and modern protein diversity

The study presents the results of analysis of protein sequence database for prokaryotic microorganisms, which revealed a conservative peptide sequence element of 11 amino acid residues in 20 loci of 16 functionally and phylogenetically differing conservative proteins from representatives of various taxa. This amino acid motif IKAVRELGLER is presumably one of the Last Universal Peptide Ancestors (LUPAs). A fragment of ribosomal RNA (part of the A-site including stems H92, H90 and H93 of the peptidyl transferase center, PTC) translated from one of the potential reading frames is likely to be a source of genetic information for this sequence. We define this m/rRNA fragment with a function of a template for LUPA synthesis as the Last Universal RiboNucleic Ancestor (LURNA). We assume that LURNA and the peptides translated from its sequence were a source of the modern diversity of peptides.