Nucleoside Phosphorylation by Phosphate Minerals

Abstract

2؉ (PO 4 ) 2 (OH) 4 ).Based on their behavior in the formamide-driven nucleoside phosphorylation reaction, these minerals can be characterized as: 1) inactive, 2) low level phosphorylating agents, or 3) active phosphorylating agents. Instances were detected (Libethenite and Hydroxylapatite) in which phosphorylation occurs on the mineral surface, followed by release of the phosphorylated compounds. Libethenite and Cornetite markedly protect the ␤-glycosidic bond. Thus, activated nucleic monomers can form in a liquid non-aqueous environment in conditions compatible with the thermodynamics of polymerization, providing a solution to the standard-state Gibbs free energy change (⌬G°') problem, the major obstacle for polymerizations in the liquid phase in plausible prebiotic scenarios.In prebiotic scenarios biopolymers can be thought of as condensation products of abiotically formed monomers. Polymers (polysaccharides, peptides, and polynucleotides) will not spontaneously form in an aqueous solution from their monomers because of the standard-state Gibbs free-energy change (⌬G°'), as critically reviewed in Ref.(1). Thermodynamic considerations impose that amino acid polymerization or the formation of phosphodiester or glycosidic linkages will be spontaneous only under highly dehydrating conditions. Thus, either (i) life did not arise in aqueous environments, or (ii) pre-genetic polymerizations required activated monomers.In the polymerization process of nucleic acids extant organisms activate the monomers by converting them to phosphorylated derivatives and then utilize the favorable free energy of phosphate hydrolysis to drive the reaction. Does this present day process mimic spontaneously occurring prebiotic reactions, thus representing a sort of biochemiomimesis descending from ancient pathways, or should it be considered a fully novel cellular invention?The Source of Phosphate Is a Problem-Early studies on the condensation of water-soluble phosphates to polyphosphates and on the phosphorylation, condensation, or polymerization of biomolecules with polyphosphates have been reviewed (2, 3). Most of the phosphorus in the early Earth would have been in the form of water-insoluble minerals like apatites. Therefore, the origin of the water-soluble (poly)phosphates required for prebiotic evolution has long been a mystery (2). Yamagata et al. (3) showed that volcanic activity produces water-soluble phosphates through partial hydrolysis of P 4 O 10 , providing at least a partial solution to their origin. However, as pointed out, phosphates from hydrolysis of polyphosphate would precipitate to the sea bed as insoluble salts.The phosphorylation of biological molecules has been explored through several different routes. Phosphonic acids have been proposed as a source of biophosphates (4). For the phosphorylation of nucleosides, two early reports described the preparation of uridine phosphates by heating uridine with inorganic phosphates in an aqueous environment (5) and the effects of condensing agents on this reaction (6). ...

Formamide and the origin of life

“…Formamide chemistry allows the formation of acyclonucleosides in non-demanding conditions [29]. As for the next step toward (pre)genetic complexity, formamide chemistry also carries on phosphorylation of nucleosides [30].…”

“…In the presence of a phosphate source at high temperature in formamide nucleosides are phosphorylated [30]. 4 .…”

“…The chemical correlations between the condensation of formamide into nucleic bases and the present-day cellular biosynthetic pathways for nucleic acids are remarkable and were discussed in detail [27]. The correlation between the [27] and to the closed-ring phosphorylation of nucleosides [30]. The abiotic synthesis of nucleosides was reported [28,158].…”

“…Formamide condensation affords all the necessary nucleic bases and acyclic nucleosides [26,27,29], allows the efficient phosphorylation of nucleosides in every possible position of ribose [30], also yielding cyclic phosphate forms. In water, purine 3 ,5 cyclic nucleotides polymerize to oligomers [31] which may non-enzymatically ligate affording long RNA molecules [129,130].…”

Intercalation as a means to suppress cyclization and promote polymerization of base-pairing oligonucleotides in a prebiotic world

“…The ability of RNA to catalyze reactions is exemplified by natural and artificial ribozymes that promote a wide variety of chemical reactions (4) as well as the observation that the catalytic core of the ribosome is comprised of RNA (5). Despite the attractiveness of the RNA world as a hypothetical stage of early life, it remains unclear how RNA [or a predecessor of RNA (6-11)] would initially have been synthesized without the aid of protein enzyme catalysis.Several distinct proposals have been presented for the abiotic origin of the first RNA polymers (10,(12)(13)(14)(15)(16)(17). Perhaps the most notable is that of Ferris and coworkers, in which mineral surfaces are used to locally concentrate and promote the polymerization of ligation-activated mononucleotides, an approach that allows formation of single-stranded RNA strands up to ca.…”