Determination of the structure of symmetric coiled-coil proteins from NMR data: application of the leucine zipper proteins Jun and GCN4.Protein Eng. 1993 Aug; 6(6):557-64.PE
Previous attempts to determine the solution structures of homodimeric 'leucine zippers' using nuclear magnetic resonance (NMR) spectroscopy have been impeded by the complete symmetry of these coiled-coil molecules, which makes it impossible a priori to distinguish between intra- and intermonomer dipolar connectivities. Consequently, a number of ad hoc approaches have been used in an attempt to derive tertiary solution structures of these molecules from the NMR data. In this paper we present a more rigorous approach for analysing the NMR spectra of symmetric coiled-coil proteins. This analysis is based on calculations of intra- and intermonomer interproton distances in the recently determined crystal structure of the GCN4 leucine zipper [O'Shea, E.K., Klemm, J.D., Kim, P.S. and Alber, T. (1991) Science, 254, 539-543] and in symmetric coiled-coil models of the leucine zippers of GCN4 and the human oncoprotein Jun which we constructed using a dynamic simulated annealing approach. This analysis has enabled the formulation of a set of rules for interpreting the NMR spectra of symmetric coiled-coil proteins and has also led to the prediction of novel dipolar connectivities which we demonstrate in a 2-D NMR spectrum of the homodimeric Jun leucine zipper.