THE CRYSTAL-STRUCTURES OF RUBISCO AND OPPORTUNITIES FOR MANIPULATING PHOTOSYNTHESIS

The crystal structures of four species of Rubisco in a number of compl exes have been solved to high resolution. The data have been used with some success to rationalize mutagenesis strategies, identify residues involved in the reaction cycle and, of particular concern, understand the basis for the ability of these enzymes to discriminate differenti ally between CO, and O-2. However, a detailed comparison of these stru ctures indicates that there are significant differences in the positio ns of critical regions of the protein that may influence the outcome o f catalysis and have certainly influenced the conclusions of investiga tors. For example, the C-terminus of the L-subunit of the inactive dim eric enzyme from Rhodospirillum rubrum has a quite distinct motif comp ared to the same segment of the activated hexadecameric Rubisco from c yanobacteria or plants, It is plausible that this is yet one more regi on of the protein that adopts different conformations depending on whe ther the active site is vacant or occupied by co-factors, bisphosphate substrate or analogues.