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GADV
PROTEIN WORLD HYPOTHESIS
ON THE ORIGIN OF LIFE
PRESENTED BY
ADAM.S
AMULYA KUMAR
DR. KENJI IKEHARA
INTRODUCTION
The concept of RNA as a primordial molecule can be found in papers by
Francis Crick and Leslie Orgel,as well as in Carl Woese's 1967 book The
Genetic Code.
The phrase "RNA World" was first used by Nobel laureate Walter Gilbert in
1986,
RNA World hypothesis is widely accepted still now, as an idea by which the
origin of life might be explained. But, there are many weak points in the
hypothesis.
In contrast, Ikehara(2002) proposed a more reasonable [GADV]-protein
world hypothesis or GADV hypothesis, suggesting that life originated from
the protein world, which was formed by pseudo-replication of [GADV]-proteins.
DRAWBACKS OF RNA WORLD HYPOTHESIS
It is very difficult to prebiotically synthesize nucleotides, building blocks ofRNA, since nucleotides are rather complex organic compounds composed ofsugar, nucleobase and phosphate.
Nucleotides are unstable underthe conditions on the primitive earth. Infactnucleotides have not been detected in meteorites.
RNA could not be self replicated due to the self-discrepancy between RNAcatalysts with stable tertiary structure and RNA templates without structures.
Even if RNA were self replicated, it is also quite difficult for the self-replicatedRNA to carry genetic information because genes would never be formed byrandom polymerization of nucleotides.
It is not statistically expected for RNA randomly polymerized in the RNA worldto encode a functional water-soluble globular protein since genes are organizedby a linear arrangement of triplet base sequences or codons encoding thecorresponding amino acids.
It is also quite difficult to explain evolutionary processes of the fundamental lifesystem , composed of genes, genetic code, and proteins according to RNA worldhypothesis, since the capability of RNA for self –replication is not relevant tothe genetic code or triplet codon sequences for protein synthesis.
GADV HYPOTHESIS
GADV : The four amino acids – Gly [G], Ala [A], Asp [D], and Val [V].
It is a novel hypothesis for the origin of life, assuming that life on the
earth originated from "[GADV]-protein world", not from the "RNA world"
(see Ikehara's review, 2002).
The [GADV]-protein world is constituted from peptides and proteins
with random sequences of four amino acids (glycine [G], alanine [A],
aspartic acid [D] and valine [V]), which accumulated by pseudo-
replication of the [GADV]-proteins.
GADV hypothesis, suggesting that life originated from the protein
world, which was formed by pseudo-replication of [GADV]-proteins
STRUCTURE
Glycine(G) Alanine(A)
Aspartic acid(D)Valine(V)
PROPERTIES OF [GADV ]-AMINO ACIDS
G,A,D & V are simple organic compounds having one hydrogen atom ,
positive amino & negative carboxylic groups, and a side chain at α-carbon
atom, and all of them are easily synthesized in Miller’s discharge
experiments.
In addition, enough amounts of [GADV]-amino acids could be
accumulated on the primitive earth , since the amino acids are enough
stable for a long time under prebiotic heat conditions.
Moreover, peptide bond, which is formed between group of one amino
acid and carboxyl group of other amino acid, has a planar character,
which is favorable for folding polypeptide chain into regular secondary
structures and successively into tertiary structures, pre requisitely
required to form catalytic centre on the surface of tertiary structure.
MILLER’S EXPERIMENT
ZERO-ORDER PROTEIN STRUCTURE HYPOTHESIS
Structure formability is the same for any protein of the same
amino acid composition, that was
randomly selected for assembling.
This means that every protein synthesized by random peptide
bond formation among amino acids in the amino acid
composition could be folded into similar but into different
structures.
Proteins can have the same amino acid composition but
different sequences.
We call such a specific amino acid composition that is
favorable for protein structure formation “protein 0th-order
structure”.
ZERO-ORDER PROTEIN STRUCTURE HYPOTHESIS
In other words, according to this concept, entirely
new proteins could be produced at a high
probability in the absence of any genetic function if
proteins can be synthesized in the specific amino
acid composition.
PSEUDO REPLICATION AND PROTEIN ZERO ORDER
STRUCTURE
EXPLANATION
The reason is because proteins composed of roughly
equal amounts of [GADV]-amino acids satisfy the four
conditions (hydropathy, α-helix, β-sheet, and turn/coil
formabilities) for folding polypeptide chains into water-
soluble globular structures.
GC-NSF HYPOTHESIS ON CREATION OF GENES ON THE
PRESENT EARTH
JUSTIFICATION OF GADV HYPOTHESIS ABOUT
THE ORIGIN OF LIFE
GADV hypothesis is consistent with three general
principles for the emergence of significant organization.
General Principle 1: From Simple to Complex Molecules.
General Principle 2: From Random to Well-organized
Processes
General principle 3: From Catalytic to Genetic Functions
A POSSIBLE EVOLUTIONARY PATHWAY OF THE LIFE
SYSTEM
COMPARISION
Emergence of Life
POSSIBLE STEPS TO THE EMERGENCE OF LIFE
1. [GADV]-protein world was created by pseudo-replication of
[GADV]-proteins, route 1 route 2 Int. J. Mol. Sci. 2009, 10
1535 which were generated by random polymerization of
[GADV]-amino acids in the absence of any gene.
Formation of the [GADV]-protein world by pseudo-replication
of [GADV]-proteins introduced the first life on the primitive
Earth.
2.The GNC primeval genetic code was created through a
specific interaction between [GADV]-amino acids and GNC-
containing oligonucleotides.
3.The most primitive single-stranded (GNC)n gene was created
by random concatenation of GNC.
4. After the emergence of the first double-stranded (GNC)n
gene, [GADV]-proteins were produced, according to the codes
of diverse (GNC)n genes created from both sense and anti-
sense codon sequences.
5. Genes, genetic code, and proteins co-evolved from (GNC)n
primeval genes, GNC primeval genetic code, and [GADV]-
proteins, respectively.
As the results, the modern life system was created comprising
(NNN)n genes, the universal genetic code, and modern
proteins, transformed through primitive (SNS)n genes, SNS
code, and SNS-encoding proteins, respectively.
POSSIBLE STEPS TO THE EMERGENCE OF LIFE
PREBIOTIC SYNTHESIS
• GADV AA SYNTHESIS
• GADV P SYNTHESIS
GADV PROTEIN WORLD
GADV AA SYNTHESIS GADV P
•GADV P WITH GADVP
NUCLEOTIDE SYNTHESIS WITH GADV P
• OLIGONUCLEOTIDE SYNTHESIS WITH
GADVP
PSEUDO ORDER REPLICATION
SYNTHESIS OF BUILDING BLOCKS LED
TO THE EMERGENCE OF LIFE
WITHOUT HELP OF GENETIC
FUNCTIONS
ESTABLISHMENT
OF GNC PRIMEVAL
GENETIC CODE
CREATION OF
FIRST RNA GENE
CREATION OF GENETIC
SYSTEM
OQOL 2014 (AT INTERNATIONAL INSTITUTE FOR ADVANCED STUDIES, KIZUGAWA-SHI, JULY
12 (SAT.)-13 (SUN), 2014) [GADV]-PROTEIN WORLD HYPOTHESIS ON THE ORIGIN OF LIFE,
KENJI IKEHARA NARA STUDY CENTER, THE OPEN UNIVERSITY OF JAPAN, FELLOW OF
INTERNATIONAL INSTITUTE FOR ADVANCED STUDIES, JAPAN (ORAL PRESENTATION).
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