ABSTRACT
Bacteriophage morphogenesis is a model
system for investigating sequential molecular assembly. The Mu phage is one of
the most classical Myoviridae. Although it is well known as a mobile genetic
element, the details of its morphogenesis remain unclear. Analysis of
conditional lethal mutants and genome analysis of the Mu phage have suggested
that genes 42, 43, 44, 45, 46, 47, and 48 are essential for its baseplate
assembly. Since we have already reported X-ray structures of the products of
genes 44 (gp44) and 45 (gp45), we here tried to purify the remaining Mu phage
baseplate subunits, gp42, gp43, gp46, gp47, and gp48, to investigate the
baseplate assembly process. In the case of gp42 expression, the transformed E.
coli cells showed growth inhibition after induction and no gp42 fractions were
observed. However, gp43, gp46, gp47, and gp48 were successfully expressed and
purified, although gp48 could not be applied to further analysis, because the
amount of soluble fraction was very low. Based on analytical ultracentrifugation,
we concluded that gp43 formed a monomer, gp46 was a monomer, and gp47 occurred
as both a monomer and dimer in solution. Moreover, we found that gp43 and gp45
formed an intermediate complex in the baseplate assembly process.