Clostridial Structure

Recently Jensen and co-workers have determined the structure of a clostridial-type ferredoxin obtained from Micrococcus aerogenes (47). One of the two apparently identical iron-sulfur clusters is illustrated in Fig. 2. The structure is compatible with a model with iron and labile sulfide at alternate comers of a cube. This accounts for the equivalence of these moieties in the protein. Another 8-iron-8 labile sulfur ferredoxin, from Clostridium acidiurici, similarly contains two independent iron-sulfur clusters per molecule (48). Strahs and Kraut (49) had earlier discovered... 

Fig. 9. A proposed structural configuration for the polynuclear iron-sulphur complex in clostridial ferredoxin.

Lebeda, F. J Umland, T. C Sax, M. Olson, M. A. (1998). Accuracy of secondary structure and solvent accessibility predictions for a clostridial neurotoxin C-fragment. J Protein Chem 17,311-8. 

FIGURE 16-6 Structures of Fe — S Protein-Active Sites, (a) Ferredoxin. (From E.-I. Ochiai, Bioinorganic Chemistry, Allyn and Bacon, Boston, 1977, p. 184.) (b) Clostridial ferredoxin. (Reproduced with permission from E. T. Adman, L. C. Sicker, and L. H. Jensen, J. Biol. Chem., 1973, 248, 3987.) (c) A model for the structure of the Fe Sg active unit. (Reproduced with permission from E.-I. Ochiai, Bioinorganic Chemistry, Allyn and Bacon, Boston, 1977, p. 192.)... 

Fig. 2. Structure and active site of clostridial neurotoxins. The upper panel shows the structure of CNTs, and the segments that show significant homology between the different serotypes are in black (Minton, 1995). The highest homology is shown by a short segment corresponding to the amino acid residues 216-244 in TeTx. This segment contains the zinc-binding motif of metallo-proteinases (zincins) and it is dissimilar to the consensus sequence of the metzincin metallo-proteinase family (Jiang and Bond, 1992)...

Kriegistein KG, Henschen AH, Weller U, Habermann E (1991) Limited proteolysis of tetanus toxin. In Eur. J. Biochem. 202 41 -51 Lebeda FJ, Olson MA (1994) Secondary structural predictions for the clostridial neurotoxins. Proteins 20 293-300... 

Neurons in primary cultures are extremely sensitive to poisoning by clostridial toxins (Habermann et ai, 1988 Williamson et ai, 1996). Moreover, primary neuronal cultures mimic many basic features of neural tissue in vivo, providing much easier access of toxins to neuronal membranes and synaptic structures. By applying clostridial toxins to primary cultured neurons it is also possible to study the possible role of the target proteins in axon elongation, synaptogenesis or neuronal survival. 

Figure 9 Construction of plasmid pKE4-9SH. The promoter region and the clostridial hydrogenase structure gene were amplified by PCR. Both fragments were ligated at their BamHI restriction sites and cloned into the shuttle vector pKE4.

Chaddock, J.A. and Marks, P.M. 2006. Clostridial neurotoxins structure-function led design of new therapeutics. Cell. Mol. Life Sci. 63 540-551. 

If iron is such an important structural determinant of ferredoxin, it might be expected that apoferredoxin and the iron-sulfide protein could exhibit different conformations. Such differences are not obvious from the ORD spectra in the far ultraviolet peptide absorption region (Fig. 22) native clostridial ferredoxin has a secondary structure which upon... 

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