Biogenesis of Cytochrome

The absorption spectrum of purified cytochrome b displayed maxima at 560 nm, 417 nm, and 278 nm in the air-oxidized form and at 561 nm, 530 nm, and 429 nm in the dithionite-reduced form (Fig. 13). The ratio of the absorbance of the protein part at 278 nm to the absorbance of the heme part at 417 nm was 0.72. Iron determination gave the following molar absorbance coefficients  

The heme was readily extracted from the protein with acid-acetone. The absorption spectrum of the reduced pyridine ferrohemochrome shows maxima at 557 nm, 526 nm, and 420 nm, indicating that the heme is a protoheme. These spectrophotometric properties of purified N, crassa 

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Although the biogenesis of cytochrome b has not been closely examined in yeast, studies on Neurospora crassa have shown that in this organism, both the mitochondrial and cytoplasmic protein-synthesizing systems contribute to the cytochrome b complex. Cytochrome b probably contains two polypeptide types of molecular weight 30,000. Inhibition studies have shown that only one of these is translated on mitochondrial ribosomes (see Chapter 5). 

Biogenesis of Cytochrome Oxidase and Cytochrome b in Neurospora crassa... 

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