We raised the antibody against the red alga LHCI not only because it was available, but also because the chromophytes, the taxonomic group of V.
It seems clear that each of the bands immunodecorated by anti-LHCI corresponds to a single LHCI polypeptide and not a dimer.
Other dimers might form with a number of photosystem I (PSI) proteins due to the close association of LHCI with the PSI subunits that compose the PSI-LHCI holocomplex (Wollman et al., 1999; Jansson, 1999).
An additional possibility might be that one of the bands could be another LHC-type protein possessing immunological similarities to LHCI, such as the fucoxanthin chlorophyll a/C binding proteins (FCPC) found in chromophytes or light-harvesting complex II (LHCII) proteins.
The LHCII family of polypeptides is closely related to LHCI, performing similar functions in photosystem II to those performed by LHCI in PSI.
The immunoprecipitations provide additional evidence that the LHCI polypeptides are being synthesized on the cytoplasmic ribosomes in the slug.
The results of the pharmacological experiments, the immunoblots, and the immunoprecipitations, taken together, provide substantial evidence that LHCI is the identity of some of the plastid proteins that are synthesized in the presence of CAP.
However, in addition to the results presented here, other circumstantial evidence for the transfer of the LHCI genes between alga and slug is available in several characteristics of the association.
litorea, the origin of LHCI is known; if the gene has been transferred, the transfer occurred between two multicellular eukaryotes and represents a case of tertiary endosymbiosis.