Cellulose-Protein Complexes in Plant Cell Walls 



R. D. Preston ^ 



Introduction 



The walls of living plant cells consist in the main of a mixture 

 of polysaccharides and their derivatives organized in such a way as 

 to be chemically stable while allowing the mutual displacements 

 necessary in the dimensional changes associated with growth. Ex- 

 cept in the fungi, which will not be dealt with here, the structural 

 element of these walls is the polysaccharide, cellulose, whose con- 

 stitution will be examined below. This substance takes the form of 

 long threads known as microfibrils, some 100-200 A wide (depend- 

 ing on the plant species— see refs. in Preston, 1952) and about half 

 as thick (Preston, 1951) (Fig. 1), which are often oriented, either 

 very roughly or with precision ( Fig. 2 ) . Both the synthesis and the 

 orientation of these microfibrils must involve proteins, and it is the 

 aim of this article to inquire how far present evidence will allow us 

 to go in defining the cellulose-protein complex which may be in- 

 volved. With few exceptions, those cell walls which have been 

 examined have been found to contain proteins (Thimann and 

 Bonner, 1933; Allsopp and Misra, 1940; Myers et al, 1956; Bishop 

 et al., 1958; Northcote et al., 1958) and, though in some preparations 

 much of the protein is derived from cytoplasmic debris, there is 

 no doubt that some part of it occurs in the wall itself. Occasional 

 reference has been made to the inclusion in cell-wall preparations 

 of electron microscopically visible particles which appear to be 

 cytoplasmic ( Myers et al., 1956 ) . 



It seems probable that the protein content of the wall sensu 

 strictii is low, perhaps not more than a few per cent. A cellulose- 

 protein complex is to be expected only during cellulose deposition, 

 after which most of the protein will be resorbed. Even this small 

 percentage remainder in the wall is therefore significant. 



' University of Leeds, Leeds, England. 



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