Peptococcus aerogenes

Fig. 2. Protein backbone representations of (a) the 2[4Fe-4S] ferredoxin from Peptococcus aerogenes, (b) the proposed structure of the FA/FB-binding protein of PSl based on the 4 A crystsd structure (25), and (c) the [3Fe-4S][4Fe-4S] ferredoxin from Sulfolo-bus acidocaldarius. Ligands to clusters Fa and Fb, important residues as well as the loop extension (see text) EU e highlighted in darker gray.

Fig. 3. Sequence comparison of the FA/FB-binding subunits of PSl from tobacco and the RC of green sulfur bacteria with that of the 2[4Fe-4S] ferredoxin from Peptococcus aerogenes. Cysteine ligands to the right-hand cluster in the three structures of Fig. 2 (i.e., cluster Fb for the case of the FA/FB-protein) are marked by open boxes Emd residues ligating the left-hand cluster by hatched boxes.

Figure 26 X-Ray structure of the active site of the 8Fe ferredoxin of Peptococcus aerogenes...

Arrangement is according to the atomic number of the reacting element. Currently Peptococcus aerogenes. 

Figure 3. Amino add sequence of Peptococcus aerogenes ferredoxin.

Adman, E. T., Watenpaugh, K. D., and Jensen, L. H. (1975). NH---S hydrogen bonds in Peptococcus aerogenes ferrodoxin, Clostridium pasteurianum rubredoxin and Chromatium high potential iron protein. Proc. Natl. Acad. Sci. U.S.A. 72,4854—4858. 

Fe-xS] ferredoxins, 33 54-55 rubredoxin, 33 44-51 hydrophobic effect, 33 60-62 significance, 33 40-44 metal complexes of, 7 218-220 model complexes, catalysis by, 33 61-62 Peptococcus aerogenes ferredoxin, structure, 38 242, 244-245... 

From the biological area, iron-sulfur clusters in biomolecules such as rubredoxin mononuclear Fe-S clusters (Rao et at., 1972), plant-type ferredoxin 2Fe-2S clusters (Johnson, 1975) and bacterial-type ferredoxin 4Fe-2S clusters (Thompson et at., 1974) are readily distinguished from one another by their Mossbauer spectra. The temperature dependence of relaxation effects can provide information about the types of internuclear interaction and can even lead to estimates of the distance between paramagnetic sites, for example, the two 4Fe-4S clusters in ferredoxin in Peptococcus aerogenes (Adman etal., 1973). 

Ferredoxins with (8Fe + 8S have also been reported in C. pasteuri-C. thermosaccharolyticum, Peptococcus aerogenes, Peptostrepto-... 

Fig. 7. Amino-acid sequence alignment for PsaC [FeS-A/FeS-B] in maize, bariey, wheat, rice, spinach, Synechococcus sp. PCC 7002, pea and tobacco and, for comparison purposes, Peptococcus aerogenes and Peptostreptococcus elsdenii. See text for discussion and data sources.

The [4 Fe-4 S] cores have been one of the most intriguing inorganic structures involved in biological systems. Carter et al. (1977) 191 demonstrated that the same basic structure is present in the two [4 Fe—4 S] centers of the 8 Fe ferredoxin of Peptococcus aerogenes (E 0 = - 400 mV)2) and in the high potential iron protein (HiPIP) isolated from the purple photosynthetic bacterium Chromatium vinosum... 

Stabilities of GDH s from microorganisms vary greatly. Whereas the NADP-GDH from Neurospora retains activity for several days at 50° and pH 7.2 (152), the NAD-GDH inactivates rapidly at raised temperatures and low ionic strengths, but is more stable in the presence of NAD (1 mAf) and the competitive inhibitor isophthalate (64). NAD-GDH s from lower fungi are also reported to be unstable (71), but those isolated from Clostridium SBj (35) and Peptococcus aerogenes (31) are stable at 50°, and so are the NADP-dependent enzymes of Salmonella... 

Promotion of protein electrochemistry by multi-charged counter ions shows several interesting features. A typical case, illustrated in Fig. 7, concerns the 2[4Fe-4S] ferredoxin from Clostridium pasteurianum. This is a low-potential electron carrier (MW approx. 6000) that carries a large overall negative charge, possibly as high as — 10 for the fully oxidized state. Structurally, it is very similar to the ferredoxin from Peptococcus aerogenes (see Fig. 14). Voltammetry at PGE... 

Four structural classes of Fe-S centre have been identified to date these are depicted in Fig. 13. All of them feature high-spin tetrahedral Fe(II) or Fe(III) coordinated typically by four sulfur donors. Apart from the monomeric centre found in proteins known as rubredoxins, they are all clusters that contain both protein donors and inorganic bridging (p) sulfido ligands. Most of our knowledge stems from studies made on the small electron-transport proteins known as ferredoxins (Fd s) and from work on model compounds. Figure 14 shows the structure of a ferredoxin isolated from the anaerobe Peptococcus aerogenes [165]. 

Fig. 14. Stereo ribbon structure of Peptococcus aerogenes ferredoxin showing the two [4Fe-4S] clusters. The C terminal and positions of the two prolines (P) are also indicated. This illustration was kindly provided by Larry Sieker (University of Washington, Seattle)...

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