The light-harvesting antenna (LH) proteins of Rhodospirillum rubrum are encoded by pufA and pufB with C-terminal extensions not present in the mature proteins. Point mutations were introduced into pufB, pufA, and both pufB and pufA so that proteins equivalent to the mature proteins were encoded. The mutants with these truncated proteins produced 3-30% of the wild-type level of LH. These findings suggest that the C-terminal extensions are required for wild-type levels of LH.