This award will support Prof. Dale Edmondson of Emory University to engage in collaborative activities with Dr. Bruno Curti and his group at the University of Milan. The researchers will focus on the enzyme glutamate synthase, which plays a key role in the assimilation of nitrogen in nitrogen-fixing microorganisms. Specifically, they will pursue the investigation of the roles of the flavin and iron-sulfur centers in the catalytic mechanisms of glutamate synthase isolated from two nitrogen-fixing bacteria, Azospirillum brasilense and Azotobacter vinelandii, the first of which is microaerophilic and associated with plant roots while the second is an aerobic free-living soil bacterium. Experimental work on the enzymes will be conducted at both Emory and Milan. Azospirillum glutamate synthase will be purified and characterized in Milan while the Azotobacter enzyme will be purified in Atlanta. The U.S. lab will provide the expertise in physical measurements on the enzyme systems. The interaction between Dr. Edmondson, who has an extensive background in areas of biophysical chemistry in general and flavoproteins in particular, and Dr. Curti's group, which has worked with the enzyme glutamate synthase for several years, should be of mutual benefit. Furthermore, it has the potential for yielding substantial results concerning the basic structure and mechanism of glutamate synthase as well as new information concerning nitrogen metabolism.