6533b82efe1ef96bd1293017

RESEARCH PRODUCT

Pigment Assembly—Transport and Ligation

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description

The ligation of pigments to proteins involved in photosynthesis appears to be strictly regulated and, in turn, to have an important regulatory impact on the biogenesis of the photosynthetic apparatus. Even so, the molecular mechanism of pigment-protein assembly is largely unknown. However, data are now accumulating on the co-translational transport of chlorophyll a proteins and the post-translational transport of chlorophyll a/b proteins into the thylakoid membrane. The molecular apparatus in the thylakoid membrane presumably occupied with protein insertion may also be involved in pigment ligation. Similarly, the last steps of pigment biosynthesis, whose location has not been fully established yet, will probably also provide a lead to the mechanism of pigment-protein assembly. Reconstitution studies with recombinant chlorophyll a/b proteins in vitro showed that the specificity of pigment binding varies—some, but not all, chlorophyll binding sites can be occupied with chlorophyll a or chlorophyll b almost equally well, and carotenoids can be structurally replaced with some other carotenoids, such as lutein with zeaxanthin. Finally, the possibility needs to be considered that pigments are assembled with proteins not only during the biogenesis of monomeric complexes but also during the assembly of multi-protein complexes of the photosynthetic apparatus.