26] Detecting metal-metal interactions and measuring distances between metal centers in metalloproteins

Abstract

Publisher Summary Even if a high-resolution structure of a metalloprotein is not available, it is possible to obtain important insights into molecular structure and function through the application of appropriate biophysical techniques. This chapter addresses one particular aspect of studying the structures of metalloproteins in solution—namely, methods and techniques to characterize the organization of metal centers in multimetal proteins. Before proceeding to the discussion of methods, a short account of the structural and functional variety of closely spaced metal atoms in multimetal proteins is given. Metals in these proteins either form well separated mononuclear complexes or are closely spaced or clustered. Metal-metal interactions occur within one protein subunit, between subunits, or between a metal cofactor or a label and an intrinsic metal atom. In this chapter, attention is focused on methods that can detect directly (physically) interacting metal atoms and that can measure distances between them. Accordingly, interaction becomes largely synonymous with proximity throughout this chapter, except that the few existing methods that can measure longer distances are also presented. Binuclear arrangements of metal ions are most frequently recognized and higher nuclearity is also observed.