Fig. 4.

Conservation and location of the L-subunit residues 149 and 309 in higher plant rubisco. (A) Coding matrix summary of ClustalW-aligned residues 300–319 in L-subunit sequences from data sets with corresponding C₃ and C₄ speciation data (11, 20, 38). (B) Structure of spinach L₈S₈ rubisco and L₈ core (L-subunits are shown in green; S-subunits are shown in blue) viewed from the top, showing central solvent channel (Left and Center), and from the side (Right). The relative locations of ¹⁴⁹Gln (white triangle) and ³⁰⁹Met (yellow triangle) in one L-subunit pair (L₂) is shown. The ³⁰⁹Met residues are located at the interface of L-subunits; the ¹⁴⁹Gln residues are positioned at the L₂–L₂ interface toward the surface of the central solvent channel. (C) View of an L-subunit pair (L₁ in green showing ribbon structural detail; L₂ in blue) showing the positioning of ¹⁴⁹Gln and ³⁰⁹Met relative to each Mg²⁺ (black sphere) and the reaction-intermediate analog 2-CABP (yellow and red ball and stick) bound to the two active sites in the dimer. The conserved active-site residues are shown for one active site. Distances (in Å) from the S atom of ³⁰⁹Met in L₂ to each Mg²⁺ and the Cα atom of the closest conserved active-site residue, ²⁹⁵Arg, are shown. (This figure was prepared with PyMOL using the PDB co-ordinates 8RUC.)