HAEM PROTEIN CONTENT AND FUNCTION IN RELATION TO STRUCTURE 28 1 



that the relation between nucleic acid and the photochemical function is 

 indirect. 



The carbohydrate and lipid fractions deserve much more mention than 

 I can give at this time. Briefly, the Newtons found (Table I) that in 

 Chromatium chromatophores, the major fraction of the carbohvdrate 

 present was in the form of a polysaccharide, the monomer unit of which 

 appeared to be galactose. The presence of a galactose moietv as a charac- 

 teristic component of the photosynthetic carbohydrate fraction in both 

 chloroplasts and chromatophores as well as a component found in galacto- 

 sidyl lipids has been well-documented by Benson and his co-workers [21, 

 22]. Progressive fragmentation of the chromatophores to smaller fragments 

 resulted in a loss of most of this polysaccharide with a corresponding 

 relative increase in lipid [11]. 



The lipids present in most photosvnthetic tissues appear to be pre- 

 dominantly of neutral or cationic type [22]. Mono- and digalactosyl 

 monoglycerides predominate. There are also some new sulpho-lipids, one 

 of which has been identified as a sulphonic acid analogue of the major 

 plant glycosyl monoglyceride [23], e.g. the structure assigned by Benson 

 et al. is i-0-(i'-deoxy-i'-sulphoketopyranosyl)-3-0-oleoylglyceride. The 

 basic phospholipid present in Chromatium appears to be almost wholly a 

 cephalin — namely, ethanolamine phosphatidyl glycerol [11]. The nature 

 of the fatty acids which are presumably bound as esters to the glycerol is 

 still unknown. This phospholipid is held to account for practically all the 

 fat in the Chromatium chromatophore [11, 24]. 



It seems evident that the photosynthetic structures elaborate special 

 lipids and carbohydrates which in many cases appear unique to the photo- 

 active particle systems. Very probably a major role involves stabilization 

 of chromatophore and chloroplast structures which contain both polar and 

 non-polar groupings. It may be mentioned that plastids from various plant 

 sources appear to contain hydrolytic enzymes (phosphatidases) which 

 attack lecithin and other lipids [25]. 



Major interest resides at present in another feature of data such as are 

 exemplified in Table I. It will be noted that cvtochrome (in this case, a 

 cytochrome complex made up of a modified haem protein called " RHP" 

 and a cytochrome of the c-type [26]) accounts for an appreciable fraction 

 of the total protein. Thus, out of 166 mg. total, there are o- 18 /tivi cyto- 

 chrome. Most of this cytochrome is the "r" component which has mole- 

 cular weight, as isolated in pure form, of 95 000 [24]. This means that 

 approximately 17 mg., or 10" ,, of the protein, is accounted for as cyto- 

 chrome. In addition, there are trace amounts of haem proteins with which 

 are associated catalase and peroxidase activities. A flavin component is 

 associated to a major extent with a yellow enzvme which can be prepared 

 from both R. rubrum [27] and Chromatium (R. G. Bartsch, unpublished) 



