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Functional capabilities of the earliest peptides and the emergence of life.

Milner-White EJ, Russell MJ - Genes (Basel) (2011)

Bottom Line: Considering how biological macromolecules first evolved, probably within a marine environment, it seems likely the very earliest peptides were not encoded by nucleic acids, or at least not via the genetic code as we know it.An objective of the present work is to demonstrate that sequence-independent peptides, or peptides with variable and unreliable lengths and sequences, have the potential to perform a variety of chemically useful functions such as anion and cation binding and membrane and channel formation as well as simple types of catalysis.These functions tend to be performed with the assistance of the main chain CONH atoms rather than the more variable or limited side chain atoms of the peptides presumed to exist then.

View Article: PubMed Central - PubMed

Affiliation: College of Medical, Veterinary and Life Sciences, Glasgow University, Glasgow G128QQ, UK. J.Milner-White@bio.gla.ac.uk.

ABSTRACT
Considering how biological macromolecules first evolved, probably within a marine environment, it seems likely the very earliest peptides were not encoded by nucleic acids, or at least not via the genetic code as we know it. An objective of the present work is to demonstrate that sequence-independent peptides, or peptides with variable and unreliable lengths and sequences, have the potential to perform a variety of chemically useful functions such as anion and cation binding and membrane and channel formation as well as simple types of catalysis. These functions tend to be performed with the assistance of the main chain CONH atoms rather than the more variable or limited side chain atoms of the peptides presumed to exist then.

No MeSH data available.


Related in: MedlinePlus

Cartoon of model low entropy environment for the emergence of metabolism via hydrothermal hydrogenation of oceanic CO2, amination of carboxylic acids and the condensation to disordered peptides. These reactions are hypothesized to take place in the outer porous iron sulfide-bearing walls to a submarine hydrothermal mound (see boxes on right of figure). Thermodynamic energy is boosted by the ambient proton-motive force. This force is assumed to have driven pyrophosphate generation, augmenting pyrophosphate of the substrate type formed by catalysis [7,8,20]. Amyloidal peptides eventually take over the role of compartment walls while retaining and nesting inorganic clusters of metals, metal sulfides and phosphate and allowing the transfer of potassium and water across these first membranes/cell walls [16,17]. In this way the properties both of the semipermeable and semiconducting membranous walls and of the catalytic propensities of the inorganic entities improve [21,22]. In this model the emergence of protometabolism from aqueous geochemistry predates transition to the RNA world [10,14,35].
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f1-genes-02-00671: Cartoon of model low entropy environment for the emergence of metabolism via hydrothermal hydrogenation of oceanic CO2, amination of carboxylic acids and the condensation to disordered peptides. These reactions are hypothesized to take place in the outer porous iron sulfide-bearing walls to a submarine hydrothermal mound (see boxes on right of figure). Thermodynamic energy is boosted by the ambient proton-motive force. This force is assumed to have driven pyrophosphate generation, augmenting pyrophosphate of the substrate type formed by catalysis [7,8,20]. Amyloidal peptides eventually take over the role of compartment walls while retaining and nesting inorganic clusters of metals, metal sulfides and phosphate and allowing the transfer of potassium and water across these first membranes/cell walls [16,17]. In this way the properties both of the semipermeable and semiconducting membranous walls and of the catalytic propensities of the inorganic entities improve [21,22]. In this model the emergence of protometabolism from aqueous geochemistry predates transition to the RNA world [10,14,35].

Mentions: Many ideas about the emergence of life have been presented [1-6]. The scenario we favor takes cognizance of the need of materials and a continual supply of energy at the appropriate magnitude to build a hatchery for life to onset. This hatchery would sustain the first metabolizing compartments and, eventually, a burgeoning population of cells [7-10]. A requirement of emergent structures is a low entropy condition whereby order in one system begets order in the next [11]. In this case, the order bestowed on emergent life and its factory is contributed by a chemostated (pH = 10 ± 1 unit) and thermostated (T = 70 °C ± 30 °C) submarine hydrothermal spring operating for tens of thousands of years [12]. The hydrothermal solution bears hydrogen as fuel, ammonia for aminations, sulfide for compartment structure and molybdenum and tungsten for catalysis [13]. Interaction of these spring waters with the early protonic and carbonic ocean, with its load of transition metals and minor concentrations of phosphate, not only produces an edifice of porous mineral precipitate but also induces a proton gradient across the margins that acts as a natural proton-motive force to drive a variety of condensations (Figure 1) [7,8]. Pore spaces on the margins of the growing hydrothermal edifice act as low entropy compartments where organic molecules are synthesized through the hydrogenation of the CO2 invading the mound margins, catalyzed by transition metals within the compartment walls (Figure 1). Products are aminated and polymerized by pyrophosphates condensed from monophosphate, perhaps with acetyl phosphate, by the ambient proton-motive force [14,15]. The inorganic compartments comprise a low entropy hatchery of life where organic reactants are forced to interact through their very proximity at low water activity [16,17]. Amino acids generated in this milieu may be condensed into peptides [18,19].


Functional capabilities of the earliest peptides and the emergence of life.

Milner-White EJ, Russell MJ - Genes (Basel) (2011)

Cartoon of model low entropy environment for the emergence of metabolism via hydrothermal hydrogenation of oceanic CO2, amination of carboxylic acids and the condensation to disordered peptides. These reactions are hypothesized to take place in the outer porous iron sulfide-bearing walls to a submarine hydrothermal mound (see boxes on right of figure). Thermodynamic energy is boosted by the ambient proton-motive force. This force is assumed to have driven pyrophosphate generation, augmenting pyrophosphate of the substrate type formed by catalysis [7,8,20]. Amyloidal peptides eventually take over the role of compartment walls while retaining and nesting inorganic clusters of metals, metal sulfides and phosphate and allowing the transfer of potassium and water across these first membranes/cell walls [16,17]. In this way the properties both of the semipermeable and semiconducting membranous walls and of the catalytic propensities of the inorganic entities improve [21,22]. In this model the emergence of protometabolism from aqueous geochemistry predates transition to the RNA world [10,14,35].
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3927598&req=5

f1-genes-02-00671: Cartoon of model low entropy environment for the emergence of metabolism via hydrothermal hydrogenation of oceanic CO2, amination of carboxylic acids and the condensation to disordered peptides. These reactions are hypothesized to take place in the outer porous iron sulfide-bearing walls to a submarine hydrothermal mound (see boxes on right of figure). Thermodynamic energy is boosted by the ambient proton-motive force. This force is assumed to have driven pyrophosphate generation, augmenting pyrophosphate of the substrate type formed by catalysis [7,8,20]. Amyloidal peptides eventually take over the role of compartment walls while retaining and nesting inorganic clusters of metals, metal sulfides and phosphate and allowing the transfer of potassium and water across these first membranes/cell walls [16,17]. In this way the properties both of the semipermeable and semiconducting membranous walls and of the catalytic propensities of the inorganic entities improve [21,22]. In this model the emergence of protometabolism from aqueous geochemistry predates transition to the RNA world [10,14,35].
Mentions: Many ideas about the emergence of life have been presented [1-6]. The scenario we favor takes cognizance of the need of materials and a continual supply of energy at the appropriate magnitude to build a hatchery for life to onset. This hatchery would sustain the first metabolizing compartments and, eventually, a burgeoning population of cells [7-10]. A requirement of emergent structures is a low entropy condition whereby order in one system begets order in the next [11]. In this case, the order bestowed on emergent life and its factory is contributed by a chemostated (pH = 10 ± 1 unit) and thermostated (T = 70 °C ± 30 °C) submarine hydrothermal spring operating for tens of thousands of years [12]. The hydrothermal solution bears hydrogen as fuel, ammonia for aminations, sulfide for compartment structure and molybdenum and tungsten for catalysis [13]. Interaction of these spring waters with the early protonic and carbonic ocean, with its load of transition metals and minor concentrations of phosphate, not only produces an edifice of porous mineral precipitate but also induces a proton gradient across the margins that acts as a natural proton-motive force to drive a variety of condensations (Figure 1) [7,8]. Pore spaces on the margins of the growing hydrothermal edifice act as low entropy compartments where organic molecules are synthesized through the hydrogenation of the CO2 invading the mound margins, catalyzed by transition metals within the compartment walls (Figure 1). Products are aminated and polymerized by pyrophosphates condensed from monophosphate, perhaps with acetyl phosphate, by the ambient proton-motive force [14,15]. The inorganic compartments comprise a low entropy hatchery of life where organic reactants are forced to interact through their very proximity at low water activity [16,17]. Amino acids generated in this milieu may be condensed into peptides [18,19].

Bottom Line: Considering how biological macromolecules first evolved, probably within a marine environment, it seems likely the very earliest peptides were not encoded by nucleic acids, or at least not via the genetic code as we know it.An objective of the present work is to demonstrate that sequence-independent peptides, or peptides with variable and unreliable lengths and sequences, have the potential to perform a variety of chemically useful functions such as anion and cation binding and membrane and channel formation as well as simple types of catalysis.These functions tend to be performed with the assistance of the main chain CONH atoms rather than the more variable or limited side chain atoms of the peptides presumed to exist then.

View Article: PubMed Central - PubMed

Affiliation: College of Medical, Veterinary and Life Sciences, Glasgow University, Glasgow G128QQ, UK. J.Milner-White@bio.gla.ac.uk.

ABSTRACT
Considering how biological macromolecules first evolved, probably within a marine environment, it seems likely the very earliest peptides were not encoded by nucleic acids, or at least not via the genetic code as we know it. An objective of the present work is to demonstrate that sequence-independent peptides, or peptides with variable and unreliable lengths and sequences, have the potential to perform a variety of chemically useful functions such as anion and cation binding and membrane and channel formation as well as simple types of catalysis. These functions tend to be performed with the assistance of the main chain CONH atoms rather than the more variable or limited side chain atoms of the peptides presumed to exist then.

No MeSH data available.


Related in: MedlinePlus