76 STRUCTURE 



Small dense spherical bodies have been found at the base of 

 flagella of Proteus (Houwink and Van Iterson, 1950). 



On the basis of X-ray diffraction studies, Burge (1961) has 

 presented two models of the arrangement of polypeptide chains 

 within bacterial flagella. In one of these there are 3 filaments, 

 each of 19 a-helices, and in the other — 7 filaments, each of 

 7 a-helices. There is not sufficient evidence to decide between 

 these two, but the latter model is favoured. 



Astbury and Weibull (1949) found that the protein of bacterial 

 flagella gave an X-ray diffraction pattern characteristic of the 

 k-m-e-f group of proteins, i.e. it is in a group that contains both 

 contractile and structural proteins. The amino acid composition 

 of bacterial flagellar protein differs from that of true flagella in 

 that the former is said to lack cystine and tryptophan (Tibbs, 

 1957). 



It appears that no attempts should be made to draw inferences 

 about true flagella from bacterial flagella, or vice versa, at least 

 until we know more about the origin, structure and function 

 of bacterial flagella. 



