Re: Dawkins on uniqueness of bacterial flagellar motor

r norman wrote:
On Sat, 05 May 2007 09:00:16 -0500, "Noelie S. Alito"
<noelie@xxxxxxxxxxxx> wrote:

r norman wrote:
On Sat, 5 May 2007 07:57:11 -0400, "sinister"
<sinister@xxxxxxxxxxxxxx> wrote:

"r norman" <r_s_norman@xxxxxxxxxxxx> wrote in message news:bnfn339lqk39eecu2bkqn4gliso5q6dvo8@xxxxxxxxxx
On Fri, 4 May 2007 18:59:28 -0400, "sinister"
<sinister@xxxxxxxxxxxxxx> wrote:

"Noelie S. Alito" <noelie@xxxxxxxxxxxx> wrote in message
news:PIOdncYLbatBLqbb4p2dnA@xxxxxxxxxxxxxxx
r norman wrote:
On 04 May 2007 18:44:41 GMT, nmp <address@xxxxxxxxxx> wrote:

Op Fri, 04 May 2007 14:29:44 -0400, schreef r norman:

On Fri, 4 May 2007 13:25:40 -0400, "sinister" <sinister@xxxxxxxxxxxxxx>
wrote:

_The God Delusion_, p. 130: "The flagellar motor of bacteria ...
drives
the only known example, outside of human technology, of a freely
rotating axel."

What about ATP synthase? (See the 1997 Nobel in chemistry.)


If Dawkins wrote that, then he was simply mistaken. He should have
said
... one of the only two known examples ...
The other one being... ?
ATP synthase. That is exactly what the query is about.

See, for example, http://www.csun.edu/~hcchm001/wwwatp2.htm
*Bitchin'* movies!


(BTW, what are all those balls and squiggly things...?)
IIRC, this is what is going on. (Accuracy may suffer, though.)

The enzyme sits on the mitochondrial membrane.
Hmm.... Would the enzyme pre-date the adoption of the
proto-mitochondrion into eukaryotes?


<chop>


What is the orientation of the driving proton gradient wrt the axle?
How do the protons exit? (Er, assuming ATP synthase does not involve
nuclear fission....)


The enzyme does pre-date the mitochondrion. "The ATP synthase
enzymes have been remarkably conserved through evolution. The
bacterial enzymes are essentially the same in structure and function
as those from mitochondria of animals, plants and fungi, and the
chloroplasts of plants. The early ancestry of the enzyme is seen in
the fact that the Archaea have an enzyme which is clearly closely
related, but has significant differences from the Eubacterial branch.
The H+-ATP-ase found in vacuoles of the eukaryote cell cytoplasm is
similar to the archaeal enzyme, and is thought to reflect the origin
from an archaeal ancestor. "
http://www.life.uiuc.edu/crofts/bioph354/lect10.html

Damn, but scientific research is good, considering it has to
swim upstream against the paleolithic human brain.


The protons enter through an "entry port", a hole to the outside, and
bind to one portion of the machinery. That binding changes the charge
of that piece. The change in charge allows the piece to alter its
binding with its surroundings and rotate. The rotation brings the
bound proton to a different location where it can be released through
an "exit port", a hole to the other side of the membrane. The
unbinding changes the charge on the protein which changes its binding
with its surroundings.

Shhh! I hear someone sneaking up with an ID explanation....


At the same time, all this change in charge and binding of the
protein causes other changes that allow the protein to accept an ADP,
transfer energy to it to convert it to ATP, and then release the ATP.
The energy comes from the fact that energy difference of the proton
binding in a region of high proton concentration and unbinding in a
region of low proton concentration. That is, the proton moves from a
region of high concentration to low which releases free energy. That
energy is captured in the binding/unbinding process and transferred to
the changing conformal states of the protein. The energy is then
transferred to the ADP to allow it to combine with phosphate to form
ATP.

I confess I've already forgotten the ADP-ATP cycle I learned in
my Bio 101 refresher course a few years ago.


The system also works backwards. It can split ATP and use the energy
to drive the protons "uphill", from low concentration to high. There
are bacteria that use this system to convert ATP energy to a proton
gradient whose energy can then be used to drive other cell functions
like ion transport.


Reduce/reuse/recycle.

Thank you!


Noelie, with the mind like a steel...sieve
--
"I am always ready to learn, although I do not always like being taught."
--Winston Churchill





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Relevant Pages

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