From: Peter Ruest (email@example.com)
Date: Sun Sep 28 2003 - 00:55:12 EDT
> Dave Wrote:
> > Where do I find the ID
> > research that has forced a reconsideration of "Darwinism"?
> I'm no biologist so a lot in their discussions are over my head but the
> threads on flagellum seem particularly good in delineating the ID vs.
> Darwinism issues. It's been such a long thread they have two with several
> For those who are well versed in this field, if they have an opinion on
> these threads, I'd appreciate hearing it.
> Steve Petermann
I am not "well versed" in this field, but I am a biochemist and thought
you might be interested in this.
Here is a copy of a comment about the evolution of the flagellum I
posted a year ago to this list:
Date: Thu, 24 Oct 2002 06:53:24 +0200
From: Peter Ruest <firstname.lastname@example.org>
Subject: Irreducible complexity and the flagellum
Some time ago, on this list, Behe's and Dembski's use of the bacterial
flagellum as a system of irreducible complexity was dismissed with the
claim that it probably evolved out of the type III protein secretion
system. I tried to check the evidence available to support this claim.
A comprehensive review of the type III system is found in Hueck C.J.,
"Type III protein secretion systems in bacterial pathogens of animals
and plants", Microbiology and Molecular Biology Reviews 62 (1998),
The type III system investigated most thoroughly is the one of the pest
(or bubonic plague) pathogen Yersinia pestis and two other Yersinia
species. There are 10 genes showing some sequence similarity between the
Yersinia type III system and flagellar proteins (of Escherichia coli,
Salmonella typhimurium, and Bacillus subtilis). All of these flagellar
proteins belong to the basal body of the flagellum which is inserted
into the cytoplasmic (inner) membrane. According to Hueck's drawing, the
basal body of the flagellar system consists of the MS (outer) and C
(inner) rings, encased in what I call the bearing, and the ATPase
attached on the cytoplasmic side. The basal body constitutes (together
with other components) the export system for flagellar constituents and
the driving machinery for flagellar rotation. The corresponding Yersinia
proteins also belong mostly to the part of the type III system
presumably embedded in the cytoplasmic membrane. At least 30 other
proteins of the flagellar system, comprising the flagellar hook, the
connection (P ring) of the hook to the basal body, the bearing (L ring)
of the hook within the outer membrane, and the flagellum proper, have no
homologs in the type III system. The Yersinia type III system, as well,
comprises at least 25 other proteins having no homologs in the flagellar
system. The 10 presumed homologs (or partial homologs) are as follows:
Flagellum: Length: Location: Function: Type III: Length: Function:
FliF 560 MS ring YscJ 236
FliG 331 C ring torque YscD 419
FliN 137 C ring YscQ 307
FliH 235 bearing 1 YscL 223
FliP 245 bearing 2 YscR 217
FliQ 89 bearing 3 YscS 88
FliR 261 bearing 4 YscT 261
FlhB 383 bearing 5 export YscU 354
FlhA 692 bearing 6 LcrD 704 export
FliI 456 cytoplasm ATPase YscN 439 ATPase
The flagellum proteins are those of E.coli or S.typhimurium, the type
III system proteins those of Y.pestis, Y.pseudotuberculosis, or
Y.enterolytica. The lengths are in amino acid residues. The location of
most type III system proteins is unknown, but inferred from that of the
flagellar homologs. The functions are usually unknown.
Synteny in the genome is restricted to FliP-Q-R with YscR-S-T.
The similarities between the FliP-Q-R / YscR-S-T systems and
(especially) the FliN-G / YscD-Q systems are weak.
In some cases, e.g. FliF / YscJ, the similar proteins are probably
unrelated. The FliF-like domain in YscJ may reflect their binding to
other components of the export apparatus. Systems III are unlikely to
have an MS ring analog, but may form a bridge across the periplasm to
the outer membrane.
FliI / YscN, which have ATPase activity, show similarities to the alpha
and beta subunits of the F1 component of the F0F1 proton translocating
ATPases; the most highly conserved regions are two GTP-binding domains
and the Mg2+-binding motif around the ATPase-catalytic domain. FliI
provides the energy for the export of flagellum units. The similarity
between FliI and YscN appears to be due to similar requirements of their
common ATPase functions.
Thus, the flagellum and the type III export system are two very complex
systems composed of a few dozen specific proteins, of which 25-30% show
some sequence similarities between the two systems. The 10 similar
proteins constitute the majority of the proteins found in all type III
export systems, as well as the flagellar basal body, whereas the parts
of the type III systems lying outside the cytoplasmic membrane show
homologies to different export systems, such as the type II secretion
systems and other transport pathways, but not to the flagellar system.
Hueck therefore suggests that the type III system may have evolved from
a combination of a flagellar basal body and a type II secretion system.
Notice that he doesn't propose that the flagellar system arose from a
type III export system!
In any case, the similarities between flagellum and type III export are
very restricted, making any derivation claim highly speculative. Whether
the sequence similarities which do exist derive from divergence from
common ancestral genes or from functional convergences remains equally
Does this situation "explain" the flagellum and demonstrate that it is
not "irreducibly complex"? I doubt it. The claim remains to be
-- Dr. Peter Ruest, CH-3148 Lanzenhaeusern, Switzerland <email@example.com> - Biochemistry - Creation and evolution "..the work which God created to evolve it" (Genesis 2:3)
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