| Bacteriophage tails, despite differences in their morphology, all play a key role in host recognition and DNA injection. It is widely believed that the tail, especially the baseplate/tail tip, has to undergo conformational change and protein rearrangement during infection. This change has been observed in both the long, contractile tail of T4 and the short tail of T7. In contrast, little is known about this aspect of the long, non-contractile tail of bacteriophage lambda. Four proteins are involved in the lambda tail tip assembly. I present evidence that gpJ, gpI, gpL and gpK are components of the tail tip complex. My results also suggest that there may be about three copies of gpI and three copies of gpL involved in the lambda tail assembly. In addition, I have successfully purified gpL, which contains eight cysteines. My results show that when the conserved cysteine at position 173, 182 or 205 is mutated to serine, the mutant protein is defective in tail assembly. However, the C212S mutant accumulates a small amount of tail. Further analysis of this mutant indicates that C212 may have roles in both tail assembly and DNA injection.;gpK is required for lambda tail assembly, but is not detected in the mature virion. Two different amber mutations were introduced into gene K. Neither of these mutants is able to complement in vivo . However, the short amber fragment is unable to assemble lambda tail whereas phage-like particles with little infectivity accumulate in the long amber fragment lysate. The results indicate that the function of gene K can be bypassed to some extent in the Kam768 mutant, but not in the Kam6 mutant. |
