Behe's Irreducible Complexity Is Refuted

Oh man..that sucks..I missed it by one year! I would have loved to have gone to that debate...as it is I only got to see Gould insult the audience and Jeremy Rifkin almost get in a fist fight with some guy from the agriculture department over genetically modified crops.

First sentence of abstractBiochem Biophys Res Commun. 2001 Oct 26;288(2):443-7. Related Articles, LinksAssociation between actin and light chains in Chlamydomonas flagellar inner-arm dyneins.Yanagisawa HA, Kamiya R.Department of Biological Sciences, University of Tokyo, Tokyo 113-0033, Japan.Inner dynein arms in cilia and flagella contain actin as a subunit; however, the function of this actin is totally unknown. Here we performed chemical crosslinking experiments to examine the interaction of actin with other subunits. Six of the seven Chlamydomonas inner-arm dynein species separated by anion-exchange chromatography contain actin and either one of the two previously identified light chains, p28 and centrin, in a mutually exclusive manner. Western blotting of chemically crosslinked dyneins indicated that actin is directly associated with p28 and centrin but not with the dynein heavy chains (HCs). In contrast, p28 and centrin both appeared to interact directly with the N-terminal half of the HCs. Thus it is likely that actin is associated with the heavy chains through p28/centrin. These light chains may well function in the assembly or targeting of the inner arm to the correct axonemal location. Copyright 2001 Academic Press.It is also present in flagellaMol Biochem Parasitol. 2004 Mar;134(1):105-14. Related Articles, LinksA novel form of actin in Leishmania: molecular characterisation, subcellular localisation and association with subpellicular microtubules.Sahasrabuddhe AA, Bajpai VK, Gupta CM.Division of Molecular and Structural Biology, Central Drug Research Institute, Lucknow 226 001, India.To study the occurrence and subcellular distribution of actin in trypanosomatid parasites, we have cloned and overexpressed Leishmania donovani actin gene in bacteria, purified the protein, and employed the affinity purified rabbit polyclonal anti-recombinant actin antibodies as a probe to study the organisation and subcellular distribution of actin in Leishmania cells. The Leishmania actin did not cross react with antimammalian actin antibodies but was readily recognized by the anti-Leishmania actin antibodies in both the promastigote and amastigote forms of the parasite. About 10(6) copies per cell of this protein (M(r) 42.05 kDa) were present in the Leishmania promastigote. Unlike other eukaryotic actins, the oligomeric forms of Leishmania actin were not stained by phalloidin nor were dissociated by actin filament-disrupting agents, like Latrunculin B and Cytochalasin D. Analysis of the primary structure of this protein revealed that these unusual characteristics may be related to the presence of highly diverged amino acids in the DNase I-binding loop (amino acids 40-50) and the hydrophobic plug (amino acids 262-272) regions of Leishmania actin. The subcellular distribution of actin was studied in the Leishmania promastigotes by employing immunoelectron and immunofluorescence microscopies. This protein was present not only in the flagella, flagellar pocket, nucleus and the kinetoplast but it was also localized on the nuclear, vacuolar and cytoplasmic face of the plasma membranes. Further, the plasma membrane-associated actin was colocalised with subpellicular microtubules, while most of the actin present in the kinetoplast colocalised with the k-DNA network.These results clearly indicate that Leishmania contains a novel form of actin which may structurally and functionally differ from other eukaryotic actins. The functional significance of these observations is discussed.References to actin and axonemes and dynein were also easy enough to find...textbooks are seldom comprehensive or up to date....

However, knocking out actin makes for some pretty nasty mutants...also major or minor component is rather arbitrary. If knocking out a gene lowers fitness (even if the organism survives) it is still a major component in its pathway.Cell Struct Funct. 1998 Oct;23(5):273-81. Related Articles, LinksRecovery of flagellar inner-arm dynein and the fertilization tubule in Chlamydomonas ida5 mutant by transformation with actin genes.Ohara A, Kato-Minoura T, Kamiya R, Hirono M.Department of Biological Sciences, Graduate School of Science, University of Tokyo, Japan.The ida5 mutant of Chlamydomonas, first isolated as a mutant lacking a subset of axonemal inner-arm dyneins, has recently been shown to lack conventional actin owing to a serious mutation in its gene. It lacks inner-arm dyneins probably because actin is an essential subunit for their assembly. In addition, male gametes of ida5 are unable to produce the fertilization tubule, a structure that contains a core of actin filament bundles. To establish that those observed deficiencies are solely attributable to the loss of actin, and to provide a basis for future studies on the actin function in this organism, we examined in this study whether transformation of this mutant with cloned actin genes can rescue the mutant phenotypes. Cotransformation of the double mutant ida5arg2 with the wild-type actin gene and arginino-succinate lyase gene that suppresses the arg2 mutation yielded several transformants that displayed increased motility. All of them were found to have acquired the introduced actin gene in the genome and the product actin in the flagella, and regained the missing inner-arm dyneins and wild-type motility. In addition, most transformants also became able to grow the fertilization tubule when mating reaction was induced. In addition to the wild-type actin gene, we also used a chimeric actin gene in which the N-terminal 12 amino-acid sequence of Chlamydomonas actin was replaced by that of the greatly divergent Tetrahymena actin. Transformants with this gene also resulted in recovery of inner-arm dynein and 70-80% of the wild-type level of motility. These results established that the lack of inner-arm dynein and the fertilization tubule in ida5 are consequences of its loss of conventional actin. Furthermore, they demonstrate that Chlamydomonas offers an excellent experimental system with which to study the structure-function relationship of actin by means of mutant analysis.

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No, it's not. Lowered fitness indicates a reduction in system function, NOT loss of minimal function. If minimal function is retained, the system is still operational and the "missing part" is not a required part.

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Then you clearly must not consider any of the various muscular dystrophies as a result of mutations in various parts of the dystrophin, utrophin etc. complex to be particularly important either though they almost universally severely impair motility of those afflicted and ultimately result in death. In any case, the lowered fitness of the actin mutants would remove those individuals from the population if not sustained by the artificial environment of the lab..thus it is still a critical function. They would not have been observed as mutants were it not for the impaired function. If you chose to view only those mutants that completely ablate a function as critical then this is a fairly esoteric view of mutation.In any case, your original point was that using textbooks you could not find references of any significant involvement of actin in cilia or flagella and this is clearly wrong.