A HAEMOPEPTIDE FROM A TRYPTIC 



HYDROLYSATE OF RHO DO SPIRILLUM RUBRUM 



CYTOCHROME C* 



By S. Paleus and H. Tuppy 



Mcdicimka Nobelinstitutet, Biokemiska Avdelningen, Stockholm, 

 and Zweites chemisches Institut der Universitdt, Wien 



For the past few years the structure of cytochrome c has been studied with 

 the aim of relating the catalytic activity of this haemoprotein to certain 

 characteristic features of its chemical architecture. Much attention has 

 been given to that portion of the protein moiety which adjoins the prosthetic 

 group and which is supposed to contribute to a catalytically active site. In 

 previous investigations (Tuppy and Bodo, 1954; Tuppy and Paleus, 1955) 

 the sequence of twelve amino-acid residues, including two haem-bound 

 cysteine residues, has been elucidated and found to be identical in the 

 cytochromes of three different mammalian species (beef, horse and pig). 

 When, however, the homologous amino-acid sequences were also determined 

 in cytochrome c from fish (salmon), bird (chicken) (Tuppy and Paleus, 1955), 

 insect (silk- worm) (Tuppy, 1957) and from a fungus (yeast) (Tuppy and Dus, 

 1958), they appeared to be dissimilar though resembling each other more or 

 less closely. The present communication will extend this comparative 

 structural investigation to the c-type cytochrome produced by the photo- 

 synthetic bacterium Rhodospirillum rubrum, first described and subsequently 

 studied in more detail by Kamen and his co-workers (Vernon and Kamen, 

 1954; Kamen and Vernon, 1955; Bartsch and Kamen, 1958). There is a 

 twofold interest in comparative structural work of this kind. In the first 

 place, one may suppose that only those features which turn up invariably 

 in cytochromes c from different sources are likely to be essential to the 

 specific catalytic function, whereas structural differences will indicate points 

 not directly concerned with catalytic activity. Secondly, the species similari- 

 ties and dissimilarities as revealed by comparative investigations of amino- 

 acid sequences may give a clue to the genetic relation between the organisms 

 from which the proteins studied have been obtained. 



* Reprinted from Acta Chemica Scandinavica, 13, 641, 1959. 



363 



