NONHEME IRON PROTEINS 325 



With the evidence at hand it is not possible to specify the role of the 

 iron protein in Chromatium electron transfer processes. It seems 

 unlikely that the protein can serve as a ferredoxin. Inasmuch as no 

 protein with properties like those of the Chromatium iron protein 

 has been extracted from the nonsulfur purple bacteria, R. nibnim, 

 Rps. spheroides and Rps. pahistris, the iron protein may play a special 

 role in Chromatin)}! metabolism. Characterization of an iron protein 

 reductase should help clarify the possible function of Chro))iatiu))i 

 iron protein. 



SUMMARY 



A nonheme iron protein, which contains an unidentified chromo- 

 phore with properties of a substituted quinone. has been isolated from 

 Chromatium. The minimum estimated molecular weight of the protein 

 is about 11,000. The iron protein with an oxidation- reduction potential 

 of Ejn = +0.35 volt is implicated in chromatophore electron transfer 

 reactions. In the dark, reduced iron protein can reduce a part of the 

 Chromatium chromatophore cytochromes which can undergo light- 

 induced photooxidation. Thus illuminated chromatophores can cause 

 anaerobic photooxidation of added reduced iron protein. The specific 

 role of Chromatium iron protein in electron transfer reaction of the 

 organism remains to be determined. 



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