The form I Rubisco of autotrophic bacteria, algae and plants is a complex of eight large (RbcL) and eight small (RbcS) subunits. It fixes atmospheric CO(2) in the dark reaction of photosynthesis. As shown for the cyanobacterial enzyme, folding of the RbcL subunits is mediated by the GroEL-GroES chaperonin system, and assembly requires the specialized chaperone RbcX, a homodimer of ~15-kDa subunits ...
The form I Rubisco of autotrophic bacteria, algae and plants is a complex of eight large (RbcL) and eight small (RbcS) subunits. It fixes atmospheric CO(2) in the dark reaction of photosynthesis. As shown for the cyanobacterial enzyme, folding of the RbcL subunits is mediated by the GroEL-GroES chaperonin system, and assembly requires the specialized chaperone RbcX, a homodimer of ~15-kDa subunits. Here we present the 3.2-Å crystal structure of a Rubisco assembly intermediate, consisting of the RbcL(8) core with eight RbcX(2) molecules bound. The structure reveals the molecular mechanism by which RbcX(2) mediates oligomeric assembly. Specifically, RbcX(2) provides positional information for proper formation of antiparallel RbcL dimers, thereby preventing RbcL-RbcL misalignment and off-pathway aggregation. The RbcL(8)(RbcX(2))(8) structure also suggests that RbcS functions by stabilizing the '60s loop' of RbcL in the catalytically active conformation.
Related Citations:
Coupled chaperone action in folding and assembly of hexadecameric Rubisco. Liu, C., Young, A.L., Starling-Windhof, A., Bracher, A., Saschenbrecker, S., Rao, B.V., Rao, K.V., Berninghausen, O., Mielke, T., Hartl, F.U., Beckmann, R., Hayer-Hartl, M. (2010) Nature 463: 197
Structure and function of RbcX, an assembly chaperone for hexadecameric Rubisco. Saschenbrecker, S., Bracher, A., Rao, K.V., Rao, B.V., Hartl, F.U., Hayer-Hartl, M. (2007) Cell 129: 1189
Structure determination and refinement of ribulose 1,5-bisphosphate carboxylase/oxygenase from Synechococcus PCC6301. Newman, J., Branden, C.I., Jones, T.A. (1993) Acta Crystallogr D Biol Crystallogr 49: 548
Organizational Affiliation:
Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Martinsried, Germany. bracher@biochem.mpg.de
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