Morphogenesis of bacteriophage phi 29 of Bacillus subtilis: prohead restoration for DNA-gp3 packaging and assembly

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Abstract
The DNA-protein complex DNA-gp3 of phage .vphi. 29 is efficiently packaged into purified proheads with the aid of plasmid-derived gp16. The filled heads can be assembled to phage by addition of an extract providing the products for neck-tail assembly. Purified proheads lost their competence to package DNA-gp3 upon storage for 2 mo. at 4.degree. C. Competence was restored by complementation with extracts of certain mutant-infected cells, and these experiments demonstrated that late proteins were not involved; restoration obtained with 4-8-14--infected cells was indistinguishable from that obtained with 7-8-14--infected cells. The 2-8-14- and 3-8-14- extracts restored .apprx. 1/3 of the capacity to package exogenous DNA-gp3. A 1-8-14- extract restored activity to package 20.6% of the DNA-gp3 added, but phage were not produced.