Steps in the Assembly of Bacteriophage T4

Citation

King, Jonathan Alan (1968) Steps in the Assembly of Bacteriophage T4. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/X9HX-V431. https://resolver.caltech.edu/CaltechETD:etd-09242002-105334

Abstract

The formation of bacteriophage T4 has been studied by examining the phage components accumulating in cells infected - under restrictive conditions - with mutants blocked at different stages of the assembly process. Structural intermediates in the pathway for tail and tail fiber assembly have been partially characterized by serology, electron microscopy, sedimentation, and in vitro complementation behavior. Tail assembly: After the baseplate (80S) is completed, the core forms on the baseplate. The functions of genes 19, 48, and 54 are required for this conversion. The gene 18 product, a major sheath structural subunit, polymerizes on the core-baseplate (80S) and then the 3 and 15 gene products fix the sheath subunits in the polymerized form, yielding a sheathed tail (130S). Tail fiber assembly: The tail fiber (10S) is made up of 8S and 9S components. The 8S component is the product of genes 38, 37, 36 and 35. The 9S component is the product of gene 34. Two precursors to the 8S component, both also 8S, are identified. A pathway for the steps in tail fiber assembly is proposed. The tail fibers attach to the tail only after the head has joined with the tail. Particles which have not been acted upon by the gene 11 or 12 product absorb to bacteria but do not kill them. Electron microscopic observations on the state of phage heads in mutant lysates are also presented. Mutations in three genes result in the accumulation of head membranes empty of DNA. All the evidence supports the view that phage heads, tails, and tail fibers are formed independently of each other.

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