Ferredoxin crystals, clostridium

Table 3 shows the recovery and extent of enrichment in each of the various purification steps of ferredoxin from Clostridium acidi-urici by using DEAE-cellulose and ammonium sulfate fractionation (Buchanan, Lovenberg, and Rabinowitz (32)). This procedure yields crystalline preparations from all clostridia which have been tested. Various modifications are employed for the crystallization of ferredoxin from other bacteria (Figs. 1 and 2). 

Table 3. Purification and crystallization of ferredoxin from Clostridium acidi-urici ...

Crystallization of Clostridium pasteurianum ferredoxin demonstration of functional interchangeability of spinach photosynthetic pyridine nucleotide reductase and bacterial ferredoxin suggestion that both be classified as ferredoxins... 

The crystals of several clostridial ferredoxins are shown in Figure 2. It indicates some of the problems involved in the determination of the structure of the protein. The crystalline forms from different clostridial species differ, but all are very small crystals. The largest ones I have seen are these from Clostridium acidi-uiici, but even these are very small as far as a crystallographer is concerned, and unfortunately, they are multiple crystals. There has been very little work done on the structure by x-ray crystallography. One problem is the small size of the crystals the second diflSculty is the fact that it has not been possible to obtain any heavy metal replacement for these proteins. However, Jensen has gotten some information on clostridial type ferredoxin that I will discuss a httle later. The plant type ferredoxin has not been obtained in crystalline form that is suitable for any x-ray work. 

Figure 10. Crystals of Clostridium acidi-urici ferredoxin and some derivatives...

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