The Quaternary Structure of the Sheaths of Defective Phages Similar to PBS X

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Abstract
The contractile sheaths of 5 defective, PBS X-like bacteriophages from Bacillus subtilis and B. licheniformis were investigated by EM, dodecylsulfate gel electrophoresis and immunodiffusion. EM images of the extended and contracted sheaths were of similar appearance, although their lengths were different. The surface lattices of both the extended and the contracted sheaths were determined by optical diffraction. This showed that the quaternary structure of the sheaths of all 5 defective phages originated from identical surface lattices, which could be approximately expressed by the selection rules L = -2n'' + 3m and L = 9n'' + 17m for the extended and contracted sheaths, respectively. in which 6n'' = n with n = 0 or an integer multiple of 6. These results indicated that the packing of the protein subunits in these sheaths differed from those of other bacteriophages, for example T4 and Mu. The MW of the main sheath protein of the defective phages, as determined by dodecylsulfate gel electrophoresis, was approximately 50,000. This value differed from that for T4, but was similar to that of Mu. The results of immunodiffusion experiments pointed to a chemical difference between the sheath proteins of the defective phages and Mu, besides T4.

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