International Summer School
	From Genome to Life:     Structural, Functional and Evolutionary approaches
	TRIFONOV Edward University of Haifa, Genome Diversity Center, Mt. Carmel, Haifa 31905, Israel title: Early evolution: From first codons to first proteins. Evolutionary history of the triplet code is reconstructed on the basis of over 55 different criteria of amino acid chronology. Four major rules are revealed that uniquely align 20 amino acids and 64 codons in respective chronological orders of their appearance on the evolutionary scene: I. The earliest amino acids are of abiotic origin (nine of 10 amino acids synthesized in the imitation experiments of S. Miller are on the top of the list), II. New codons appear as complementary pairs, III, The new codons appear in descending order of the thermostability of the codon pairs, and IV. The new codons are simple mutational or complementary versions of the codons engaged earlier. Every codon is 1-4 step descendant of the very first codons GCC and GGC. The reconstructed codon chronology suggests that the very first oligopeptides encoded in the earliest mRNA duplexes consisted of residues belonging to two independent amino acid alphabets. Massive protein sequence analysis shows that modern proteins still carry remnants of the earliest mosaic organization. The elementary mosaic unit is estimated to be of size 6 residues. The next stage of the early evolution of proteins corresponds to the formation of the closed loops of the chains. According to polymer-statistical properties of the mixed sequence polypeptides, the optimal size for the loop closure is 20-40 amino acid residues. This loop size, indeed, is detected and well documented by analysis of protein crystal structures and protein sequences. The prototype sequences and secondary structures of the ancestral proteins, 27 to 32 amino acids in size, are derived and mapped in the known protein structures and sequences. ADDITIONAL DATA HTTP LINK: http://www.weizmann.ac.il/sb/faculty_pages/Trifonov/I_Ber.html