Towards a Structure Based Mechanism for the Function of the Carboxysome, the Prototype Bacterial Organelle

University Of Southern Mississippi, Hattiesburg MS

Investigators

Abstract

Intellectual Merit: Carboxysomes are polyhedral protein microcompartments found in many autotrophic bacteria. They are composed of a thin protein shell and are filled with 1,5-bisphosphate carboxylase/oxygenase (RubisCO). This research seeks answers to the question of the advantage these bacteria derive from packaging their carbon dioxide fixing enzyme (RubisCO) into carboxysomes. The PIs previously showed that a unique carbonic anhydrase (CA), which is tightly associated with the carboxysome shell, enhances RubisCO's catalytic efficiency by mediating what appears to be a directional transfer of abundant cytoplasmic bicarbonate to the carboxysome interior as carbon dioxide. The ability of the shell to impede diffusion of bicarbonate and carbon dioxide traps the gas in the interior, where it is fixed by RubisCO. Structural and molecular biological approaches will be combined with genetic and biochemical experiments to further elucidate structural and functional features of the microcompartment that will yield a deeper understanding of its role in microbial carbon metabolism. Broader Impacts: Given the large contribution of carboxysome-containing organisms towards carbon dioxide fixation and the impact of their metabolism on the global carbon cycle, broader implications of the work planned will be the elucidation of one of the most basic and central biochemical processes that controls the carbon cycle and influence weather and climate. Graduate and undergraduate students participating in the project will gain experience in biochemical and molecular biological research approaches. Through ongoing collaborations with scientists at this and other institutions, these students will gain an appreciation of interdisciplinary scientific approaches. The PIs will continue their practice of actively recruiting members of underrepresented groups (e.g. ethnic minorities and women) to participate in the project as undergraduate and graduate student researchers.