Design in living organisms (motors: ATP synthase)
by Jonathan Sarfati
Bacterial flagellum with rotary motor, after Ref. 1. (from The
Bacterial Flagellum, <www.arn.org/
docs/mm/flagellum_all.htm>)
In our everyday experience, we can usually tell whether something has been
designed. The main evidence is high
information content. The information content of any arrangement
is the size, in bits, of the shortest algorithm required to generate that arrangement.
This means that repetitive structures, like crystals, have a low information content,
because all that is needed is to specify a few positions, then the instructions
‘more of the same’. The difference between a crystal and an enzyme or
DNA is like the difference between a book containing nothing but ABCD repeated and
a book of Shakespeare.
On a practical level, the information specifies the many parts needed to make machines
work. Often, the removal of one part can disrupt the whole machine. Biochemist Michael
Behe, in his book Darwin’s Black Box (right), calls
this irreducible complexity.1
He gives the example of a very simple machine: a mousetrap. This would not work
without a platform, holding bar, spring, hammer and catch, all in the right place.
The thrust of Behe’s book is that many structures in living organisms show
irreducible complexity, far in excess of a mousetrap or indeed any man-made machine.
Motors: a case study
Motors are irreducibly complex, because they need many parts working together to
function. For example, an electric motor needs a power source, fixed stator, movable
rotor, and a commutator or slip rings.
ATP synthase motor, after Ref. 4. (from ATP Mechanisms Revealed,
<www.arn.org/
docs/mm/atpmechanism.htm>)
The more parts needed for a machine, the harder it is to make it smaller. Miniaturisation
is such a vital part of the computer industry, and the best human minds are constantly
working at it. And though miniaturised motors would be very useful, e.g. for unblocking
clogged arteries and blood cleaning, the number of parts makes it difficult to make
them below a certain size. But ingenious scientists are making them smaller all
the time.2
However the design in living organisms has far exceeded our most painstaking efforts.
Bacteria propel themselves using flagella (singular flagellum,
from the Latin for whip), filaments propelled by a true rotary motor. This motor
is only the size of a virus, thus far smaller than anything man-made. Yet it can
rotate at over 1000 times per second.3
But even this impressively tiny motor is not the tiniest in God’s creation.
In a paper published in March 1997, Hiroyuki Noji et al. directly observed
the rotation of the enzyme F1-ATPase, a subunit of a larger
enzyme, ATP synthase.4,5 This had been suggested as the mechanism for the enzyme’s
operation by Paul Boyer.6 Structural
determination by X-ray diffraction by a team led by John Walker had supported this
theory.7 A few months after Noji et
al published their work, it was announced that Boyer and Walker had won
a half share of the 1997 Nobel Prize for Chemistry for their discovery.8
The F1-ATPase motor has nine components—five different proteins
with the stoichiometry of 3a:3b:1g:1d:1e. In bovine mitochondria, they contain 510,
482, 272, 146 and 50 amino acids respectively, so Mr = 371,000. F1-ATPase
is a flattened sphere about 10 nm across by 8 nm high—so tiny that 1017
would fill the volume of a pinhead. This has been shown to spin ‘like
a motor’ to produce ATP, a chemical which is the ‘energy currency’
of life.9 This motor produces an immense
torque (turning force) for its size—in the experiment, it rotated a strand
of another protein, actin, 100 times its own length. Also, when driving
a heavy load, it probably changes to a lower gear, as any well-designed motor should.
ATP synthase also contains the membrane-embedded FO subunit functioning
as a proton (hydrogen ion) channel. Protons flowing through FO provide
the driving force of the F1-ATPase motor. They turn a wheel-like structure
as water turns a water wheel, but researchers are still trying to determine precisely
how. This rotation changes the conformation of the three active sites on the enzyme.
Then each in turn can attach ADP and inorganic phosphate to form ATP. Unlike most
enzymes, where energy is needed to link the building blocks, ATP synthase uses energy
to link them to the enzyme, and throw off the newly formed ATP molecules. Separating
the ATP from the enzyme needs much energy.
Note: the names of the two components are historical. The F1 unit comes
from the term ‘Fraction 1’, and the name FO (written as a
subscript capital O, not zero) is due to its being the oligomycin-binding fraction.
ATP synthase is the central enzyme in energy conversion in mitochondria (where they
are embedded into the cristae, folds in the mitochondrion’s inner
membrane), chloroplasts and bacteria. This probably makes ATP synthase the most
ubiquitous protein on Earth. Since energy is required for life, and all life uses
ATP as its energy currency (each of us synthesizes and consumes half our bodyweight
of ATP per day!), life could not have evolved before this motor was fully functional.
Natural selection by definition is differential reproduction, so requires self-reproducing
entities to start with. So even if a series of gradual steps could be imagined up
this peak of ‘Mount Improbable’, there would be no natural selection
to enable that climb.
One of the Nature articles was appropriately entitled ‘Real Engines
of Creation’. Unfortunately, despite the evidence for exquisite design, many
scientists (including the editor of Nature) still have a blind faith that
mutations and natural selection could build such machines.
Would any evidence convince evolutionists?
The famous British evolutionist (and communist) J.B.S. Haldane claimed in 1949 that
evolution could never produce ‘various mechanisms, such as the wheel and magnet,
which would be useless till fairly perfect.’10
Therefore such machines in organisms would, in his opinion, prove evolution false.
These molecular motors have indeed fulfilled one of Haldane’s criteria. Also,
turtles11 and monarch butterflies12 which use magnetic sensors for
navigation fulfil Haldane’s other criterion. I wonder whether Haldane would
have had a change of heart if he had been alive to see these discoveries. Many evolutionists
rule out intelligent design a priori, so the evidence, overwhelming as
it is, would probably have no effect.
Animations (off-site)
Related articles
References
- Behe, M.J.,
1996. Darwin’s Black Box: The Biochemical Challenge to Evolution,
The Free Press, New York.
Reviewed by Ury, T.H., 1997. Journal of Creation 11(3):283–291.
Return to text
- Hogan, H., 1996. Invasion of the micromachines. New Scientist
150(2036):28–33. Return to text
- For a good description, see Behe, Ref. 1. Return
to text
- Hiroyuki Noji et al., 1997. Direct observation of the
rotation of F1-ATPase. Nature 386(6622):299–302.
Comment by Block, S. Real engines of creation. Same issue, pp. 217–219. Return to text
- Wu, C., 1997. Molecular motor spins out energy for cells. Science
News 151(12):173. Return to text
- Boyer, P., 1993. Biochim. Biophys. Acta 1140:215–250.
Return to text
- Abrahams, J.P. et al., 1994. Structure at 2.8 Å
resolution of F1-ATPase from bovine heart mitochondria. Nature
370(6491):621–628. Comment by Cross, R.L. Our primary source
of ATP. Same issue, pp. 594–595. Return to text
- Service, R.F., 1997. Awards for High-Energy Molecules and Cool
Atoms. Science 278(5338):578–579. The third winner
is Jens Skou of the University of Aarhus in Denmark. Forty years ago, he was the
first to identify an enzyme that moves substances through cell membranes (in this
case, sodium and potassium ions). This is a key function of all cells.
Return to text
- ATP stands for adenosine triphosphate.
It is a high energy compound, and releases this energy by losing a phosphate group
to give ADP, adenosine diphosphate.
Return to text
- Dewar, D., Davies, L.M. and Haldane, J.B.S., 1949.
Is Evolution a Myth? A Debate between D. Dewar and L.M. Davies vs. J.B.S. Haldane,
Watts & Co. Ltd / Paternoster Press, London, p. 90. Return to text
- Sarfati, J.D., 1997.
Turtles can read magnetic maps. Return to text
- Poirier, J.H., 1997.
The Magnificent Migrating Monarch. Creation 20(1):28–31.
But monarchs only use the earth’s magnetic field to give them the general
direction, while they rely on the sun’s position for most of their navigation.
Return to text
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