Molecular recognition in thylakoid structure and function

In photosynthesis, light-harvesting chlorophyll molecules are shunted betwe en photosystems by phosphorylation of the protein to which they are bound, An anchor for the phosphorylated chlorophyll-protein complex has now been i dentified in the reaction centre of chloroplast photosystem I. This finding supports the idea that molecular recognition, not membrane surface charge, governs the architecture of the chloroplast thylakoid membrane. We describ e a model for the chloroplast thylakoid membrane that is consistent with re cent structural data that specify the relative dimensions of intrinsic prot ein complexes and their dispositions within the membrane. Control of molecu lar recognition accommodates membrane stacking, lateral heterogeneity and r egulation of light-harvesting function by means of protein phosphorylation during state transitions - adaptations that compensate for selective excita tion of photosystem I or photosystem II. High-resolution structural descrip tion of membrane protein-protein interactions is now required to understand thylakoid structure and regulation of photosynthesis.