Acta Univ Latv (2004) 676: 97–105

Origin of globins and a mystery of myoglobin codon root symmetry

Abstract

The amino acid sequence 49–94 of myoglobin involved in heam binding has 74 % symmetric codon roots – the second codon letters. The search for the reason of the symmetry revealed that the ancestor of globin genes was not formed by exon shuffling, but by multiplication of a 21-membered nucleotide and that it was a regular polynucleotide. The repeat unit pile of contemporary myoglobin codon root sequence posesses an inversion centre indicating that symmetry of codon roots evolved after the origin of globin gene. Its cause and possible biological functions is a mystery. A model of coding of the globin ancestor gene is suggested to be formed of identical repeat units separated by 23 introns.