The Investigation of the Proton Magnetic Resonance Spectra of Some Copper Proteins

Abstract

Of all the physical methods currently applied to the study of the structure and function of proteins in solution only nuclear magnetic resonance spectroscopy has the power to probe each and every part of the protein. Normally this results in a surfeit of information, but recent technical advances (Campbell et al., 1973; Campbell and Dobson, 1975) have made it possible to exploit the inherent potential of the method. With proteins of moderate weight, ≤ 50,000 daltons, sensitivity is no longer a problem, adequate signal-to-noise being efficiently achieved with samples having a concentration ≥ 5 x lO^-4M. Sufficiently resolved spectra can now be obtained by the employment of techniques, based on some discriminatory principle. Assignment may also be aided by such techniques but it is still laboriously achieved in most instances. For the full exploitation of the method it is desirable to assign individual resonances in the spectra to specific amino acid residues in the protein. This is currently the major problem. Although no general method has yet emerged such detailed assignments can be made in a number of instances. In this paper we describe the problems and the promise of the method by its application to azurins, plastocyanins and superoxide dismutase.