294 



Fulvio Perini 



A peptide containing 15 amino acids, obtained after peptic 

 digestion, contains the only two cysteine residues which were 

 found in this protein and the haem. The amino acid analysis 

 indicates an unusually high proportion of acidic and neutral 

 amino acids and three tryptophan residues. 



The haem obtained by silver sulfate fission^ '' appears to be 

 identical with that obtained from mammalian cytochrome c. 



Spectrally, cytochrome c-552 is different from all other algal 

 haemoproteins and more similar to mammalian cytochrome c. 



PPNR absorbs in the Soret region at the same wavelength as the 

 maximum of cytochrome c-552, therefore, preparations of this 

 cytochrome which contain PPNR could give incorrect spectral data. 



Cytochrome 55^ is far more unstable than cytochrome 552 linder 

 drastic conditions such as exposure to dilute alkali, acid, and 

 high salt concentrations. 



Methylethylketone (pH 2.0) did not remove the prosthetic group 

 from either cytochrome 552 or 55^. Treatnent with silver 

 sulfate -acetic acid yielded products which were identical with 

 haem c on paper chromatography, the product of fission from 

 cytochrome 55^ had a different absorption maximxim in acid 

 (haem 55^ = 3^0 nui; haem 552 and c = 403-^ n^i). 



The spectrum of cytochrome, 556 (fig. 2) is somewhat like that 

 of higher plant cytochrome f ^ '^ and other algal haemoproteins. 

 The pyridine haemochromogens of cytochrome 55^ and haem 556 were 

 different from products obtained from classical c- and b-type 

 corapoiinds . 



Preparations of cytochrome 552 which were homogeneous in the 

 ultracentrifuge vrere obtained. This i^as not possible with 

 cytochrome 556, however, it was prepared in a highly pvirified 

 state . 



Cytochromes b-561 and a-605 



Acetone powders of light -grown cells which had been extracted 

 for soluble cytochrome were examined in a Gary model ik apparatus 

 provided with the 1^^-62 scattered transmission attachment. This 

 made it possible to obtain difference spectra of suspensions 

 with maxima which appeared to be due to a b-type cytochrome or 



