Head Proteins from T-Even Bacteriophage: I. Molecular Weight Characterization 1

T-even bacteriophage capsid proteins were separated on 6% agarose columns by use of 6 m guanidine hydrochloride containing 5 mm dithiothreitol both to dissociate and to elute the proteins. The head capsids of T2H, T4B, T4B01, T4D, and T6r(+) contained at least three structural proteins with molecular weights of 40,000, 18,000, and 11,000 daltons, amounting to 76, 2, and 8%, respectively, of the total capsid protein. On the other hand, T2L head capsids contained only two structural proteins with molecular weights of 40,000 and 18,000 daltons (81 and 2.5%, respectively, of the total protein). A discussion of the possible role of these structural head proteins and a T-even phage head model suggesting a structural arrangement of the 40,000 dalton subunit are presented.