PHYSIOLOGY OF BACTERIAL CHROMATOPHORES 



J. W, NEWTON 



Pioneering Laboratory for Microbiological Chemistry 



Northern Utilization Research and Development Division 



Agricultural Research Service 



U. S. Department of Agriculture 



Peoria, Illinois 



Several years ago a systematic investigation of the antigenic com- 

 ponents of bacterial chromatophores was initiated with the hope of 

 detecting structjiral relationships between the bacterial particles and 

 other cellular constituents, as well as identifying any unique antigens 

 which might characterize the photochemical apparatus (1-3), The re- 

 sults of these investigations have provided some leads to possible new 

 enzymatic systems in chromatophores, especially to those systems 

 which may possess some mechanoenzymatic properties. Furthermore, 

 some of the structural data from the immunochemical work contain 

 implications for the problem of energy transfer in the photochemical 

 apparatus. 



To summarize the earlier work, it was found that photosynthetic 

 bacteria elaborated unique antigenic constituents during photosynthetic 

 growth and that these new antigens were attached to the bacterio- 

 chlorophyll-bearing components of the cell and were serologically re- 

 lated to the cell wall-membrane complex. Furthermore, the antigenic 

 substructure of the chromatophore was disulfide bonded; i,e,, the 

 antigenically reactive groups were spaced between pairs of disulfide 

 bonds in the chromatophore. When isolated chromatophore particles 

 were treated with reagents known to cause scission of disulfides, the 

 particles were quantitatively cleaved to yield serologically univalent 

 derivatives of the parent chromatophore. These results indicated that 

 chromatophores contained a repeating substructure with the "mono- 

 mers," in an antigenic sense, placed between disulfide bridges in the 

 particles. 



The wealth of literature on radiation effects on simple and complex 

 disulfides, including proteins, indicates that these bonds are very 

 susceptible to radiation cleavage (4,5), It seems possible that the 

 structural disulfides interspaced in the chromatophore particle could 

 serve as energy "sinks" for photochemical processes, Calvin and co- 

 workers (6) proposed such a mechanism for the simple disulfide lipoic 

 acid some years ago, and although the lipoic acid hypothesis has re- 



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