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Kenneth Miller's flagellar sub-sctructures

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Frank Sullivan

Jan 16, 2006, 8:06:11 PM1/16/06
I don't know who else watched Ken Miller's lecture in Ohio. I thought
it was great, and I wish that I knew of a why to download and save
streaming video to my hard drive.

Anyway, at one point he was explaining how the TTSS is homologous to 10
proteins found in the flagellum, blah blah. After he was finished, he
displayed a chart showing how the other 40 proteins or so were *also*
parts of sub-structures that had other purposes in the cell. I was
wondering if anyone knew where I could find this chart on the web. The
video quality was poor so the chart was not readible on the video.

Jan 16, 2006, 10:21:59 PM1/16/06

* 10 flagellum proteins are long-recognized homologs of the TTSS

* another 10 (rod/hook/linker/flagellar filament/cap -- all part of the
rotating tube) are either certainly or probably homologous to each
other, and the ancestral tube is probably homologous to the pilus
protein in TTSS

* About 11 flagellum proteins (in E. coli) are chemotaxis/signalling
related and have widespread homologs in all sorts of other signalling
and motility/taxis systems. Plus, they are missing entirely in some
flagellated bacteria.

* about 10 other proteins are optional, i.e. not found in all flagella

* and the remaining ~10 can be accounted for piecemeal, e.g. the motor
proteins MotA and MotB are homologous to the non-flagellar motor
proteins ExbB and ExbD, FlgJ shares a domain with a muramidase, one
domain of FliM is homologous to the entirety of FliN (and FilN has a
homolog in T3SS), FliA is a sigma factor homologous to other sigma
factors (which do regulation), FlgA is homologous to CpaB (a protein in
other secretion systems), FlhDC are homologous to SetDC, FliK is
homologous to an 11th T3SS PubMed for refs, plus: for the approximate
situation as of 2003 (which has improved since then).

...and that's about it. There are a few proteins that can't (yet) be
accounted for this way, but the last time I counted I think it was down
to 3, and they were things like chaperones.


Jan 17, 2006, 3:28:05 AM1/17/06

Does accounting for homologs in all proteins required for the bacterial
flagella mean that there was a gradual emergence of the flagella? For
example, perhaps all 40 genes were used elsewhere, but they may have
suddenly come together due to a regulatory mutation. If that was the
case, then there would have been a sudden emergence of the flagella.
Likewise, merely identifying the homologs does not explain a gradual
emergence of flagella.

Frank Sullivan

Jan 17, 2006, 2:10:16 PM1/17/06

Thanks! That's exactly what I was looking for.

Frank Sullivan

Jan 17, 2006, 2:17:53 PM1/17/06

No, but if can break a structure that has 40-50 "parts" down into, say,
6-8 sub-structures that have other uses in the cell, then it is a lot
easier to imagine how it could have evolved. That is, rather than
having 50 individual parts that come together all at once, you have 8.
In this particular case, it looks like many of the sub-structures
aren't needed at all in order to produce *some* motility function, so
speculating about a gradual evolutionary pathway becomes that much
easier. I'm reading the paper hosted on now. It's pretty
interesting but a lot of it is over my head.

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