DNA packaging and developmental intermediates of a broad host range Vibriovulnificus bacteriophage 71A-6

The structural intermediates in the capsid assembly and DNA packaging pathw ay of Vibrio vulnificus bacteriophage 71A-6, a rod-shaped double-stranded D NA podovirus, were isolated by ultracentrifugation and studied by electron microscopy, SDS-PAGE and pulsed-field gel electrophoretic analysis. Bacteri ophage 71A-6 synthesized rod-shaped capsids (mean length = 200 +/- 8 nm; me an width = 47 +/- 3 nm; n = 50) during its development. Several host protei ns that probably help in the assembly and maturation of the capsids were at tached to these capsids as spherical structures. A capsid-DNA or DNA packag ing complex that consisted of the mature capsids, DNA and a 42(.)5-kDa prot ein was also isolated. The size of the capsids increased in length and decr eased in width (mean length = 220 +/- 8 nm; mean width = 45 +/- 3 nm; n = 5 0) either during or after the DNA packaging. The capsid fractions contained about 12 phage structural proteins and eight host proteins. At least three proteins were tentatively identified: a 38(.)5-kDa major capsid protein, a 35(.)2-kDa tail protein and 42(.)5-kDa packaging initiator or terminator p rotein. The size of the bacteriophage 71A-6 genome was determined to be 143 (.)0-kb by pulsed-field gel electrophoresis. The total mass of all the matu re phage proteins corresponded to only 14(.)0% of the coding capacity of ph age genome. (C) 2001 Academic Press.