Speculations on the origin of the genetic code.
The most primitive code is assumed to be a GC code: GG coding for glycine, CC coding for proline, GC coding for alanine, CG coding for "arginine." The genetic code is assumed to have originated with the coupling of glycine to its anticodon CC mediated by a copper-montmorillonite. The polymerization of polyproline followed when it was coupled to its anticodon GG. In this case the aminoacyl-tRNA synthetase was a copper-montmorillonite. The first membrane is considered to be a beta sheet formed from polyglycine. As the code grew more complicated, the alternative hydrophobic-hydrophilic polypeptide (alanine-"arginine") was coded for by the alternating CG copolymer. This alternating polypeptide (ala-"arg") began to function as both a primitive membrane and as an aminoacyl-tRNA synthetase. The evolution of protein structure is tightly coupled to the evolution of the membrane. The alpha helix was evolved as lipids became part of the structure of biological membranes. The membrane finally became the fluid mosaic structure that is now universal.
Hartman
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Institute for Advanced Studies in Biology, Berkeley, CA 94707, USA.
D000596:Amino Acids / Q000737:chemistry / Q000145:classification; D000604:Amino Acyl-tRNA Synthetases / Q000145:classification / Q000235:genetics*; D000926:Anticodon / Q000737:chemistry; D002462:Cell Membrane / Q000502:physiology; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D005227:Fatty Acids / Q000737:chemistry; D005815:Genetic Code; D008051:Lipid Bilayers / Q000737:chemistry; D008563:Membrane Lipids / Q000737:chemistry / Q000502:physiology; D008954:Models, Biological; D009711:Nucleotides / Q000737:chemistry; D012343:RNA, Transfer / Q000737:chemistry / Q000235:genetics; D012995:Solubility
D000596:Amino Acids; D000926:Anticodon; D005227:Fatty Acids; D008051:Lipid Bilayers; D008563:Membrane Lipids; D009711:Nucleotides; D012343:RNA, Transfer; D000604:Amino Acyl-tRNA Synthetases