HEME PROTEINS 67 



containing moiety of n has been accomplished and results are consistent 

 with the assumption that one heme is attached by thioether bonds to 

 two cysteinyl residues, separated by two residues, as in cytochrome c. 

 The placement of the other heme is uncertain, as only one more 

 cysteine is available for linkage of thecovalenttype. Larger quantities 

 of protein will be needed to permit further elaboration of the peptide 

 structure as well as that for the whole protein. 



The nature of the second heme group is still in question, also. It is 

 certain that it does not differ in oxidation potential appreciably from 

 the value found by titration of the protein. 



The primary sequences for I and II, beginning at the terminal end, 

 show interesting correlations (see Table 2), Thus, for II, the sequence 



TABLE 2 



Composition of Cytochromoids 



Amino Acid Composition 

 Per Heme: 



R. ruhrum - (hys^^ HiSg Arg^ ^ ^^Pg 5 '^^^7 ^^^10 ^^'^12.5 ^^°4 



Gly^ Ala^g Val^ ^ IleUg ^ LeUg Tyrg Phe^ Met^ Cys^ 

 Try,) 



Chromatium - A.ySg His, Arg^ ^^^u ^^P(^"2)2 '^^^'g ^^^3 ^^"^17 

 Glu NH^ 2 PrOa Try, Gly,^ Ala^^ Val,^ Leu^ Ileu^ 

 Met^ Cys^ Tyr^ Phe^^) 



Rps. PalJistris - (Lys,^ His, Arg^ Asp,, Thr^ Ser^ GlUg Pro^^ 



Glyg Ala,^ Val^ Ileu^ LeUg Met^^^^^ Cys. 



Heme Peptide Sequence 



Val-Ala-Asp-Glu-Gly-Ser-Ala-Lys-Cys-His-Thr-Phe- 

 A sp-Glu-Gly-Ser-COOH 



End-Group Sequences 



R. nibrum- H^N-Ala-AspNH^-Val-Ala-Gly Glu-COOH 



Chromatium - H N-Ala-Gly-Leu/ -Ser-AspNH^ — Ala-COOH 



lieu 



