19 19 



CYTOCHROME C 357 



does not account for two of these, which are probably methionine; Akesson 

 (31) had found two molecules of this amino acid in cytochrome c. The 

 protein of cytochrome c is remarkably high in lysine, which explains the high 



TABLE IV 



Amino Acid Composition of Cytochrome c" 



Amino acid 



(Porphyrin c) 



Histidine 



Arginine 



Lysine 



Cysteine 



Tyrosine 



Tryptophane 



Glutamic acid 



Aspartic acid 



Amide nitrogen 



Leucine 



Isoleucine 



Phenylalanine 



Alanine 



Glycine 



Valine 



Hydroxyvaline J 



Total 145 (101.5% 



of total N) 



" According to Theorell and Akesson {2782). 



isoelectric point, and low in histidine and tryptophane. It is of interest that 

 cytochrome c contains nine to ten free amino groups more than correspond 

 to its lysine content; this indicates a branched arrangement of short poly- 

 peptide chains. 



Neurath {20Jt5) gives a frictional ratio of 5.4 for anhydrous, and 3.1 for 

 hydrated cytochrome c. 



On a water-air interface cytochrome c forms monolayers of 3.5 A thickness 

 at its isoelectric point {1128,1425). Alterations below pH 3 and above pH 

 12 are indicated by greater compressibility of the films. The ferric form 

 spreads more rapidly than the ferrous, while the opposite holds for hemo- 

 globin and myohemoglobin. 



Bechtold's (197,198) erroneous claims that myohemoglobin can be revers- 

 ibly transformed to cytochrome c are partly due to a confusion of cytochrome 

 c and mixed hemochromes (cf. Chapter VI, Section 2.4.4.), partly to areduc- 



33 SS 



