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ARS Home » Research » Publications at this Location » Publication #79629
Title: IN PLANTA ACTIVITY OF RECOMBINANT RUBISCO ACTIVASE ALTERED AT AN ATP BINDING SITE MEASURED BY RUBISCO ACTIVATION STATE AND INFRA RED GAS ANALYSIS

Author
item KALLIS, RUSS - SCL LIFE SCI UOFI URBANA
item KELLY, WALTER - SCL LIFE SCI UOFI URBANA
item PORTIS JR, ARCHIE
item WHITMARSH, CLIFFORD

Submitted to: Plant Physiology Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 8/6/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Site directed mutagenesis at an ATP binding site altered in vitro properties of rubisco activase. Previously reported data on apparent dissociation constants for ADP and ATP show reduced affinity for nucleotide. Greater dissociation of inhibitor ADP is consistent with observations that 42kD Arabidopsis recombinant rubisco activase Q111D and Q111E mutants activase Rubisco to a greater rate and extent at several ADP/ATP ratios compared to recombinant wild type. Consistent with this, we observed a high activation state and low RuBP levels in planta in an activase deficient mutant Arabidopsis rca complemented with 42dK recombinant Arabidopsis Rubisco activase Q111E. It has been suggested that rubisco activase activity influences the induction kinetics of photosynthesis by limiting the approach of photosynthesis to a new steady state level following an increase in PFD. Therefore, we compared the response of photosynthesis to increases in PFD in both wild-type and Arabidopsis rca plants complemented with 42kD Arabidopsis Rubisco activase Q111E, Q111D, and Q111S. We observed that rca expressing Q111D, Q111E, and Q111S had a faster approach to steady state photosynthesis following an increase in PFD compared to wild type. Finally, Rubisco activation has been implicated in the heat sensitivity of photosynthesis. Therefore we compared the heat stability of the recombinant enzymes to the wild-type. Loss in ATPase activity after treatment at 40 degrees C for one hour was greatest for Q111D at 85 percent, comparable for 42 rwt and Q111S at 38 and 35 percent, and lowest for Q111E at 18 percent. Whether these differences extend to the effect of heat on photosynthesis in planta is under current study.