HEME PROTEINS 65 



TABLE 1 



Composition ofc-Type Cytochromes* 



Amino Acid Composition 

 Per Heme: 



R. rubrum - (LySj^^ HiS2 Asp-j^^ ThPg Ser^ Gly^ Pro^ Glyg Ala^g 



Valg lieu Leu Met Cys^ Tyr Phe Try^^N ; 9 amides 



Chromatium - (Lys^^ His^ Argg Asp^^ ^^^^12 ^^^15 ^^^3 ^^°18 

 ^1^29 ^^^35 ^^^9 "^^17 ^^V ^^% 'ry^l3 ^^^0 



Rps. Pahistris- CLys^^ms^ ^^Pl5 "^^^8 ^^^2 ^^^8 ^^^3 ^^^12 

 Ala^g Valg Ileu^ LeUg Cys^ Tyr^ Phe^ Try^) 



Heme Peptide Sequence: 



R. nibnim - H^N-Ser-Lys-Cys-Leu-Ala-Cys-His-Thr-Phe-Asp-Glu-Gly- 

 Ala-Asp NH2 -Lys-COOH (Residues 14-28) 



End-Group Sequences ; 



Glu 

 -Asp- 

 (NH,) 



R. rubrum - H N-Glu-Gly-Asp-Ala-Gly-Ala Lys-COOH 



Chromatium - H^N-Glu 



* These data have been taken both from published articles (9,10,11) and unpub- 

 lished observations by K. Dus, H. de Klerk, and M. D. Kamen. 



tives— either the excited chlorophyll oxidizes the cytochrome, after 

 loss of an electron, or it oxidizes the cytochrome before loss of an 

 electron. Either possibility is consistent with the data now at hand, 



(c) &-Type cytochromes. Very little is known about these heme pro- 

 teins, except that they exist in amounts which may approach those of 

 the c-type cytochromes. Only one instance of a solubilized specimen 

 has been reported (16). Attempts to link the6-type cytochromes of the 

 purple photosynthetic bacteria with a conventional function in the elec- 

 tron transport chain, coupled to phosphorylation either in dark or light, 

 have been frustrated by the simultaneous occurrence of the o-type 

 cytochromes and cytochromoids, spectrochemical characteristics of 

 which mask expected spectral shifts which might be ascribed to &-type 

 cytochromes, 



(d) Catalases and peroxidases. Practically nothing is known about 

 these types of heme proteins, except that their presence is evident 



