STRUCTURAL AND CHEMICAL ARCHITECTURE OF HOST CELLS 



115 



Powell, 1954) permitted the clarification of tlie chemical structure and role 

 of these relatively bizarre accumulation products (Park and Strominger, 

 1957). A typical nucleotide of this type is presented in formula (IV). 



o- 



OH OH 



O- 



COCH, 



NH H OH 



0=C^ ^CH 



N^^.CH 



OH 



OH OH 



C-C-C-C-CH2-O-P-O-P-O-C-C-C-C-C-CHPH 

 I II I 



00 O 



0=C — C— CH3 



o 



,1. 



D-alanine 



D-glutamate 



, I 

 L- lysine 



D-alanine 



D-alanine 



(IV) 



Many variations on this structure are known, particularly in peptide 

 composition. In E. colt, for example, L-lysine is replaced by diaminopimehc 

 acid. It appears that the nucleotides are the bearer of the sugar-peptide 

 fragments which are incorporated as units into cell wall. Penicilhn in some 

 way blocks the synthesis of these units into cell wall, permitting the cell to 

 grow through and out of a wall which can no longer cover the enlarging 

 surface. Outside of its restraining corset, the cell lyses in unsuitable osmotic 

 conditions and dies. It should be noted that the lactyl ether of A^-acetyl 

 glucosamine has not yet been discovered in animal or plant tissues. The 

 existence of this exclusively microbial product and associated compounds 

 may then be considered to account for the lack of toxicity of peniciUin to 

 animal cells, since limiting membranes of animal cells are evidently con- 

 structed of somewhat different materials. Nevertheless, a unit similar to the 

 lactyl ether, namely, the pyruvyl derivative, siahc acid (see Fig. 2), is a 

 constituent of erythrocyte stroma and of ganghosides, v,diich are probably 

 organized in the surface membranes of nerve cells. One might ask if this type 

 of structure does not represent a general feature of hmiting membranes, and 

 if the various mucoproteins which contain siahc acid are not either degrada- 

 tion products of such membranes or products which accumulate as a result 

 of their inefficient incorporation into cell membranes. The increased appear- 

 ance of serum mucoproteins in infections perhaps suggests the former 



