Characterization of the carbon fixation enzyme, RubisCO, in a psychrophilic Chlamydomonas, isolated from Lake Bonney, Dry Valleys, Antarctica

Jenna Dolhi, Patrick Feasel, and Rachael Morgan-Kiss

Microbiology, Miami University

Ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) catalyzes the first reaction in the Calvin-Benson-Bassham (CBB) cycle. While arguably one of the most important enzymatic reactions on earth, incorporation of inorganic carbon into sugars is extremely inefficient owing to low turn-over rates and the competing oxygenase reaction. Thus, RubisCO has long been recognized as an attractive candidate for genetic manipulation in order to improve its efficiency. Here we characterize RubisCO from an environmental isolate, the Antarctic green alga, Chlamydomonas raudensis UWO241. Our hypothesis is that RubisCO is a likely target for adaptation of the photosynthetic process to the permanent cold. We compare UWO241 RubisCO to that of a closely related mesophilic alga, C. raudensis SAG49.72, to investigate RubisCO adaptation. Here we present temperature profiles for carboxylase activity in crude and purified fractions of psychrophilic and mesophilic enzymes. Predicted amino acid substitutions in the large and small subunits in the psychrophile RubisCO compared with C. reinhardtii are also discussed.

e-mail address of presenting author: dolhijm@muohio.edu