The Increase of Efficiency of RuBisCO

Abstract

Carbon dioxide (CO2) is the primary source of carbon for life on Earth. As such, the efficient incorporation of CO2 into organic matter is of significant importance. Ribulose‐1,5 bisphosphate carboxylase/oxygenase (RuBisCO), sequenced from the cyanobacteria Synechococcus PCC6301, is a 64.8 k‐Da photosynthetic enzyme involved in the oxidation‐reduction process of carbon fixation, assimilating inorganic carbon into bioavailable organic carbon. RuBisCO is composed of two subunits: a large L chain and a smaller S chain, with a length of 467 amino acids. Each chain consists of eight sub‐chains and weighs 51.87 k‐Da and 12.93 k‐Da respectively. RuBisCO, the most abundant protein in the world, is slow‐reacting, fixing about 3–10 CO2 molecules each second per molecule of enzyme. During the catalysis of RuBisCO, the formation of an active site intermediate is able to react with either CO2 or Oxygen (O2). Approximately 25% of the time, RuBisCO will bind with O2 instead of CO2. This misbinding has a significant impact on the enzyme's effectiveness within the Calvin cycle as well as other photosynthetic processes. The functionality error of RuBisCO means that the enzyme exhausts large quantities of ATP in order to process the O2 and then attempt to bind to CO2. Minimizing RuBisCO's intermediate active site's availability can reduce the occurrence of photorespiration. While variations to RuBisCO exist between different photosynthetic species, all species experience inefficiencies due to oxygenation to some extent. Efforts to discover more efficient carboxylation through random mutagenesis of RuBisCO lead to the discovery of a mutant that catalyzes the carbon fixation reaction with greater speed, accuracy, and precision. The resultant mutated RuBisCO was chosen through selection in E. coli. Mutations in the C‐terminal loop 6 region and a substitution mutation at 331 of valine to alanine, both within the large subunit, decreased the specificity factor by almost 40%. RuBisCO's enlarged specificity factor could potentially benefit the development and growth of many different species of plants. The potential increase in crop productivity could have a substantial impact on global food distribution. Walton High School SMART Team has designed a 3D model of RuBisCO using JMOL to investigate the relationship between structure and function.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.