152 M. D. KAMEN 



sively (10,19,30). Its properties, which are t5^pical of many "c" 

 cytochromes in photosynthetic organisms, are exhibited in Table I. 



The facultative bacteria yield these proteins readily upon treatment 

 with warm trichloroacetic acid as in the Keilin-Hartree procedure, 

 and can be purified in the same manner as mammalian cytochrome c 

 (19,38). However, they are noticeably more labile than their mam- 

 malian analogs and can be obtained in better yield with less dena- 

 turation by use of less drastic methods (19,20). In R. ruhrum and 

 R. spheroides, most of the cytochrome "c" appears to be loosely bound 

 and extractable. There also is a fraction which is tightly bound 

 to the particles and resists extraction with aqueous systems just as 

 do the chloroplast hematins. 



There is some evidence that cytochromes of the "h" type are pres- 

 ent in the chromatophores of the facultative bacteria. However, 

 only one such hematin compound has been characterized (38). 



A remarkable new type of hematin compound, as yet unclassified, 

 has been observed which is distributed generally in the facultative 

 bacteria (19,38). Its properties are hsted in Table II. This compound 

 displays the spectroscopic properties of a compound of the myo- 

 globin type and shows, as well, an ability to form a CO complex in the 

 reduced form. Nonetheless, it yields hemochromogens with spectra 

 like those formed from a typical cytochrome c. The redox potential 

 lies in the region normally attributed to hemoglobins or cytochrome 

 b. It is clear that this hematin compound cannot be classified (at least, 

 HO far) in any of the common categories of the iion porphyrin pro- 

 teins. 



The enzymatic properties of this compound are also remarkable 



TABLE II. Some Properties of R. rubruni Yellow Pigment (38) 



Classification Hybrid 



Stability Thermostable, slowly denatured at low pH 



Autoxidation Rapid 



Reaction with CO in reduced form Forms CO complex 



Absorption maxima (reduced) 550, 423 m/i (no beta band) 



Absorption maxima (oxidized) 640, 490-500, 393 mjw 



£o'(pH7) ~0.1 to -1-0.15 mj* 



Reduced pyridine hemochromogen Spectroscopically identical with that ob- 

 tained from mammalian cytochrome c 



Reduced cyanide hemochromogen Spectroscopically identical with that ob- 

 tained from mammalian cj^tochrome c 



