title: Protein modules conserved since LUCA.
abstract: Universal scale of the sequence conservation has been recently introduced based on omnipresence of the protein sequence motifs across species. A large spectrum of short sequences, up to eight residues has been found to reside in all or almost all prokaryotic organisms. By this discovery a principally novel quantitative approach is introduced to the problem of reconstruction of the last universal common ancestor (LUCA). The most conserved elements (protein modules) with defined structures and sequences harboring the omnipresent motifs are outlined in this work, by combining the sequence and protein crystal structure data. The structurally conserved modules involve 25-30 amino acid residues and have appearance of closed loops, loop-n-lock structures. This confirms earlier conclusions on the loop-fold structure of globular proteins. Many of the topmost conserved modules represent the primary closed loop prototypes, that have been derived by whole genome sequence searches. The data presented, thus, make a basis for further developments toward the earliest stages of protein evolution.
authors.affiliation: Genome Diversity Center, Institute of Evolution, University of Haifa, Haifa 31905, Israel.
authors.forename: Yehoshua
authors.initials: Y
authors.lastname: Sobolevsky
authors.forename: Edward N
authors.initials: EN
authors.lastname: Trifonov
mesh_terms: D000595:Amino Acid Sequence; D000604:Amino Acyl-tRNA Synthetases / Q000737:chemistry / Q000235:genetics; D000818:Animals; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics; D017124:Conserved Sequence / Q000235:genetics*; D026942:DNA Topoisomerases / Q000737:chemistry / Q000235:genetics; D019143:Evolution, Molecular; D006801:Humans; D008969:Molecular Sequence Data; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry* / Q000235:genetics*; D016415:Sequence Alignment
chemical_list: D018797:Cell Cycle Proteins; D011506:Proteins; D026942:DNA Topoisomerases; D000604:Amino Acyl-tRNA Synthetases