HEAD MORPHOGENESIS GENES OF THE BACILLUS-SUBTILIS BACTERIOPHAGE SPP1

We have identified and characterized the phage cistrons required far a ssembly of SPP1 heads. A DNA fragment containing mast of the head morp hogenesis genes was cloned and sequenced, The 3'-end of a previously i dentified gene (gene 6) and eight complete open reading frames (7 to 1 5) were predicted. We have assigned genes 7, 8, 9, 11, 12, 13, 14 and 15 to these orfs by correlating genetic and immunological data with DN A and protein sequence information. G7P was identified as a minor stru ctural component of proheads and heads, G11P as the scaffold protein, G12P and G15P as head minor proteins and G13P as the coat protein. Cha racterization of intermediates in head assembly, which accumulate duri ng infection with mutants deficient in DNA packaging or in morphogenet ic genes, allowed the definition of the head assembly pathway. No prot eolytic processing of any of the head components was detected. Removal of G11P by mutation leads to the accumulation of prohead-related stru ctures and aberrant particles which are similar to the assemblies form ed by purified G13P in the absence of other phage-encoded proteins. Th e native molecular masses of G11P and G13P are about 350 kDa and large r than 5000 kDa, respectively (predicted molecular masses 23.4. kDa an d 35.3 kDa, respectively). G13P, upon denaturation and renaturation, a ssembles from protomers into some prohead-related structures. The orga nization of the DNA packaging anti head genes of SPP1 resembles the or ganization of genes in the analogous regions of phage lambda and P22. (C) 1997 Academic Press Limited.