Metalloproteins to Membrane Proteins: Biological Energy Transduction Mechanisms
Structural analyses of two macromolecular systems, the metalloprotein nitrogenase and the integral membrane protein MscL (mechanosensitive channel of large conductance), are discussed within the context of energy transduction mechanisms. Nitrogenase catalyzes the ATP dependent reduction of dinitrogen to ammonia during the process of biological nitrogen fixation, while MscL is a stretch activated (mechanosensitive) channel that opens and closes in response to changes in lateral tension applied to membranes. Although nitrogenase and MscL have very different structures and functions, they both mediate the coupling of two energetic processes. From these studies, it is suggested that effective coupling of two processes by transduction proteins occurs through conformational states common to each process.