Active Rubisco in Biotechnology

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Active Rubisco is the proportion of enzyme that is catalytically competent and can contribute to the process of CO2 fixation by carboxylation (Carfts-Brandner and Salvucci 2000). For Rubisco to remain activated, it requires the ATPase Rubisco activator enzyme known as RCA to facilitate the removal of sugar phosphates from the active site. In the absence of a molecular 3D structure of RCA, understanding the precise interaction details between RCA and Rubisco remains obscure. Until the 3D structure details are available, researchers deal with RCA as an ATPase from AAA+ protein family (Neuwald et al. 1999). This protein family members are known to use a region close to the C-terminal domain known as ‘Sensor II’ for recognizing it’s substrate (Li et al. 2005). The knowledge concerning the mechanism of action for RCA activity and the conformational changes that occur when interacting with Rubisco are all gathered from various mutagenesis studies that have targeted different positions of this protein (Portis et al. 2008). One of those studies demonstrated that the conformational changes in the position 89-94 of Rubisco are responsible for closing the active site during the reaction (Duff et al. 2000). At this point, RCA can access the sugar phosphate-binding site (Portis 2003). Rubisco region between 89-94 binds through electrostatic forces to RCA region 311-314, causing a conformational change in RCA leading to exposing the ATPase active site on RCA. ATP hydrolysis by RCA promotes the movement of its C-terminal Sensor II domain that is believed to interact with the sugar phosphate (Li et al. 2006). The ATPase activity of RCA is sensitive to ATP/ADP ratio in the surrounding environment, which in turn determines wither the reaction is ... ... middle of paper ... ...ity of PRK alone to E. coli would be a marker for un-functional Rubisco screen. This system has been successfully demonstrated with strong evidence that this E. coli strain, susceptible to PRK, does not produce false-positive results (Mueller-Cajar et al. 2007). The use of biotechnological approaches is suggested in this study to overcome these problems through gathering the information from various studies that compares different Rubisco sequences with known affinities to CO2 and mutagenesis studies on RCA activity. This data will be analyzed and used to optimize the sequence of Rubisco active site or RCA Sensor II domain according to chemical binding affinities between amino acid residues and substrates. A fast reliable bacterial testing system, depending on Escherichia Coli, will be used for determining the functionality and kinetics of chimeric Rubisco or RCA.

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