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The archaea also use a unique form of electron transport in methanogenesis (Schafer 2004). The viral SF3 superfamily (Leitão 2015) helicase tree shows variants active on both RNA and SNA substrates, consistent with an origin in the RNA era (Caprari et al. Supporting the notion of subunits, a beta-chain of ATP synthase is homologous to a hepatic lipoprotein receptor (Martinez et al. Fig 1b2: Left: Rotary action of ATPsynthase, shown centre. Right: Evolutionary tree of viral RNAhelicase includes forms active in both RNA and single and double-stranded DNA viruses (Caprari et al. Respiratory electron transport occurs in both aerobic and anaerobic organisms and the terminal oxidases, iron-sulphur proteins and flavin-binding polypeptides all show evolutionary trees reaching back to the common ancestor of the three domains, implying terminal oxidases predate oxygenic photosynthesis.The extremely ancient origin of the rhodopsin family of heptahelical receptors can be seen from the ultra-primitive archael photosynthesis in Halobacteria, which relies on direct coupling between photo-stimulated chemiosmotic H-dependent ATPsynthase universal to the chemiosmotic coupling of electron transport to ATP production is a rotary motor which appears to have evolved from two separate subunits, one of which has been proposed to be a helicase (Doering et al. Hexameric helicases are found both in the SF3 superfamily in viruses (Hickman & Dyda 2005) and the MCM helicases are critical to replication forks in diverse organisms from humans to archaea (Fletcher et al. The fact that many components of archaeal electron transport are significantly different in structure from those of bacteria implies these evolved separately and that archaeal electron transport is not simply a more recent result of horizontal transfer (Schafer 2004).This initial tree forms a good representation of the evolution of higher plants and fungi, so the remainder of the article will examine the tortuous route from the last common ancestor, through the eucaryotes to metazoa, and ultimately to humanity, language and culture.This article seeks to be a real time account of the discovery processes showing us in ever-incteasing detail, the nature of the tree and its many tangled interactions, both at the genetic and organismic level. 2009), giving rise to the RNA era, while at the same time providing a free energy source based on proton transport across membranous microcellular interfaces resulting from fatty acids also being concentrated above their critical aggregate concentration.This article is a fully referenced research review to overview progress in unraveling the details of the evolutionary Tree of Life, from life's first occurrence in the RNA-era, to humanity's emergence and diversification, through migration and intermarriage.
Following a phase of biogenesis possibly emerging directly from cosmic symmetry-breaking (King 1978, 2004), based on spontaneous prebiotic RNA synthesis (Powner et. 2009, 2010) recent research suggests that the last universal common ancestor (LUCA) of all life on the planet may have arisen before the first cells, from a phase interface between alkaline hydrogen-emitting undersea vents and the archaic acidified iron-rich ocean (Martin and Russel 2003) in which differential dynamics in membranous micropores in the vents managed to concentrate polypeptides and polynucleotides to biologically sustainable levels (Baaske et. This is suggested by fundamental differences in their cell walls and other details of evolutionary relationships among some of the oldest genes.SECIS is an unusual hairpin loop structure which has varying forms in archaea and prokaryotes with both forms appearing in eucaryotes, but they have a common feature of a highly conserved hairpin loop forming an RNA translational catalyst, which literally takes over some of the ribosomal RNA function, binding to the selenocysteine t-RNA and coupling selenocysteine to the nascent protein chain, as shown in fig 1c2.It is clear that this unique piece of genetic software engineering evolved in LUCA because the wobble positions of three other essential amino acid t-RNAs, lysine, glutamine and glutamic acid (those with two wobble positions XAA-XAG, the fourth set being amber and ochre stop codons), all depend on a modified 2-seleno-uridine base to function and this has to be generated from selenophosphate, which in turn is generated by selenophosphate synthetase.Fig 1b3: Evolutionary trees for two components of the electron transport chain, Fe-S proteins (left) and flavin-binding polypeptides (right archaea lower right Homo sapiens upper left), span the three domains of life (Schafer et al. It has also been proposed, on the basis of the highly-conserved commonality of transcription and translation proteins to all life, but the apparently independent emergence of distinct DNA replication enzymes in archaea/eucaryotes and eubacteria, that the last universal common ancestor had a mixed RNA-DNA metabolism based on reverse transcriptase, pinpointing it to the latter phases of the RNA era (Leipe et. The validity of the RNA-era concept and the capacity for RNAs to be both replicating informational and active ribo-enzymes is emphasized by the continuing dependence of the ribosome on r RNA rather than the protein components demonstrated by the 3D realizations of the two subunits in fig 1c1, which show that the r RNA molecules are still carrying out the central task of protein assembly with only minor modification due to the 'chaperoning' proteins, despite 3.8 billion years of evolution. (2002) have found that the amino acids used in sections of genes common to life which are believed to originate with LUCA show amino acid distributions reflecting the relative abundance of such amino acids in primitive synthesis, indicating that the first translational genes used the amino acids which were spontaneously available, consistent with my original hypothesis on origin of the genetic code in Biocosmology.A specfic model of the evolution of the ribosome envisages that the smaller subunit which binds to and moves along the m RNA began first as an RNA-based RNA helicase which was essential to avoid the RNA era ending in non-replicating double stranded hairpins (Zenkin 2012).