NONHEME IRON PROTEINS AND CHROMATIUM 

 IRON PROTEIN 1 



ROBERT G. BARTSCH 



Department of Chemistry , University of California 



San Diego, La Jolla, California 



Relatively little attention has been given nonheme iron proteins as 

 such in photosynthetic bacteria. Heme proteins, especially the cyto- 

 chromes, are produced in large amounts by these bacteria (1) and, at 

 least in Chromatiuni, nonheme iron is also found in appreciable 

 amounts. Newton and Newton (2) showed the acid- soluble iron content 

 of Chro matin m chromatophore fractions to be in the range of 0.7 to 

 1.7 mg/g protein. On a comparative biochemical basis these electron 

 transfer particles might be expected to contain nonheme iron proteins 

 which play a role in electron transfer reactions. Enzymes of the iron 

 flavin type such as succinic dehydrogenase (3) and NADH- cytochrome 

 c reductase (4), as well as the less completely characterized iron- 

 containing proteins hydrogenase (5) and ferredoxin (6-8), may be 

 chromatophore constituents. The first three enzymatic activities are 

 found in various chromatophore preparations, while ferredoxin has 

 been isolated from photosynthetic bacteria in soluble form (8), In this 

 report is described a nonheme iron protein isolated in relatively 

 large amounts from Chromatium . 



EXPERIMENTAL PROCEDURE 



Purification of Protein. 



Chromatium iron protein has been purified as a byproduct in the 

 course of Clironiatium cytochrome purification (9-11); no comprehen- 

 sive purification procedure is yet available. The general procedure 

 we have used is as follows, A crude cell-free extract, usually pre- 

 pared by sonication, was centrifuged at 25,000x5" for 1 hour to remove 

 cell debris plus large chromatophores. The protein precipitated by 

 30-60 g ammonium sulfate per 100 ml extract was collected, dissolved 

 in buffer, and dialyzed free of salts. The protein fraction was chroma- 



1 The work reported here was performed in the laboratory of Professor M. D. 

 Kamen with support from the National Institutes of Health (Grant No.C-5992), 

 National Science Foundation (Grant No. G-19642), and the C. F, Kettering 

 Foundation. 



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