The Role of Structural Intersubunit Microheterogeneity in the Regulation of the Activity in Hysteresis of Ribulose 1,5-Bisphosphate Carboxylase/Oxygenase

Abstract

Many enzymes are composed of subunits with the identical primary structure. It has been believed that the protein structure of these subunits is the same. Ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO) comprises eight large subunits with the identical amino acid sequence and eight small subunits. Rotation of the side chains of the lysine residues, Lys-21 and Lys-305, in each of the eight large subunits in spinach RuBisCO in two ways produces microheterogeneity among the subunits. These structures are stabilized through hydrogen bonds by water molecules incorporated into the large subunits. This may cause different effects upon catalysis and a hysteretic, time-dependent decrease in activity in spinach RuBisCO. Changing the amino acid residues corresponding to Lys-21 and Lys-305 in non-hysteretic Chromatium vinosum RuBisCO to lysine induces hysteresis and increases the catalytic activity from 8.8 to 15.8 per site per second. This rate is approximately five times higher than that of the higher-plant enzyme.

Improved analysis of C4and C3photosynthesis via refinedin vitroassays of their carbon fixation biochemistry

“…The use of non-pure RuBP further compromised the quantification of k cat c (2.2s −1 with pure RuBP versus 1.3s −1 with non-pure RuBP) and the calculated activation status of Rubisco (75±2% with pure RuBP versus 83±3% with non-pure RuBP). Use of non-pure RuBP should therefore be avoided in order to avoid underestimating the carbamylation status ( Rowland-Bamford et al , 1991 ; Anwaruzzaman et al , 1996 ; Ruuska et al , 2004 ; Sulpice et al , 2007 ) and activity ( Rintamäki et al , 1988 ; Uemura et al , 2000 ) of Rubisco.…”

Plant-like substitutions in the large-subunit carboxy terminus of Chlamydomonas Rubisco increase CO2/O2 Specificity

“…The analogous Lys-305 of the spinach enzyme interacts with the carboxy terminus via a single hydrogen-bond (Fig. 1 ) and a P305K substitution in Chromatium vinosum Rubisco causes an 80% increase in carboxylation catalytic efficiency [ 16 ]. It is thus likely that the addition of V341I and R305K substitutions to the D470P/T471A/I472M/K474T quadruple mutant would confer kinetic constants that are more like the flowering-plant enzymes.…”

RUBISCO: Structure, Regulatory Interactions, and Possibilities for a Better Enzyme

“…However, because a variety of land-plant Rubisco enzymes cannot be genetically engineered, conclusions must be based primarily on alterations of the Synechococcus or Chlamydomonas enzyme (86,93). The major limitation to the phylogenetic approach is, once again, deciding which of the many divergent regions are worth analyzing (e.g., 86,93,140). Nonetheless, by combining this approach with others, two large-subunit regions have been investigated intensely.…”