A cold-active rubisco without small subunit exhibits the highest turnover number towards CO2
July 14-18, 2019
Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) has long been a primary engineering target to improve photosynthesis efficiency due to its slow catalytic rate towards CO2. However, the difficulty in finding and engineering a fast Rubisco over the past decades bring about the confusion that whether a constraint exists in Rubisco's catalytic potential. Here, we screened 29 Rubiscos with different forms, which were originated from microbes from different genera in different living environments. A highly active form II Rubisco was found. It showed 4.2- and 2.8-fold increased specific carboxylation activity and turnover number compared with those of Rubisco from Synechococcus PCC7002, the known fastest Rubisco in nature. Interestingly, even in ice-cold water (0oC), it was able to fix CO2 at a rate which was 63% of that of 7002 Rubisco at 37oC. Integration of this highly active Rubisco into S. elongatus PCC7942 improved its specific growth rate and photosynthetic rate by 50% and 100%, respectively. Structural analysis revealed that it was a hexamer with three pairs of large subunit homodimers around a central 3-fold symmetry axis. The loop 6 and C terminus were crucial for its high carboxylation activity. The lack of small subunit and no need for any chaperon for its heterologous expression/assembly making its further manipulating in plant and molecular engineering in E. coli much easier. Figure
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Zhen Cai, Junli Zhang, Jie Zhou, Wei Zhang, Fan Yang, Yin Li, and Guoxia Liu, "A cold-active rubisco without small subunit exhibits the highest turnover number towards CO2" in "Biochemical and Molecular Engineering XXI", Christina Chan, Michigan State University, USA Mattheos Koffas, RPI, USA Steffen Schaffer, Evonik Industries, Germany Rashmi Kshirsagar, Biogen, USA Eds, ECI Symposium Series, (2019). https://dc.engconfintl.org/biochem_xxi/51