Structural and Functional Characterization of Cyanoglobin

Pennsylvania State Univ University Park, University Park PA

Investigators

Abstract

Lecomte, Juliette 0091182 Cyanobacteria are oxygenic prokaryotes now known to produce a hemoglobin (Hb) related to certain bacterial and protozoan hemoglobins. Although in nitrogen-fixing cyanobacteria, hemoglobin appears to protect the nitrogenase complex from oxidative damage, in non-nitrogen-fixing cyanobacteria, such as Synechocystis sp. PCC 6803, the role of hemoglobin remains a mystery. The immediate goal of this project is to study the relationship between structure and reactivity in the hemoglobin of Synechocystis. Biophysical methods (NMR spectroscopy, optical spectroscopy, centrifugation, redox potential measurements) and biochemical methods (genetic manipulations, immunostaining techniques, phenotypic characterization, site-directed mutagenesis) will be applied to 1) investigate Synechocystis Hb in vivo; 2) determine its three-dimensional structure in solution; and 3) analyze the molecular determinants of its heme coordination and electrochemical properties. Comparison will be made to other hemoglobins to develop an atomic level understanding of heme reactivity in cyanobacterial globins and situate these proteins in their evolutionary context. The globin family of proteins has representatives in practically all kingdoms of organisms. In vertebrates, hemoglobins and myoglobins are responsible for the transport and storage of oxygen but in primitive organisms, the functional roles of globins include oxygen scavenging, delivery, sensing, and detoxification, and management of nitrosative stress. Cyanobacteria such as Synechocystis can be manipulated experimentally like other prokaryotes and subjected to genetic methods. Thus they are ideally suited for studies of ancient hemoglobins. A description of the function of cyanobacterial hemoglobins is expected to provide fundamental insight in the biochemistry of organisms essential in the global cycling of carbon and nitrogen. The project will serve as a support in teaching activities such as a biological chemistry course and an NMR course. It will provide excellent opportunities for undergraduate and graduate student training in biophysical and biochemical methods and foster multidisciplinary interactions.