Biophys J, July 2000, p. 526-535, Vol. 79, No. 1

Flexibility of the -Spectrin N-Terminus by EPR and Fluorescence Polarization

Department of Chemistry, Loyola University of Chicago, Chicago, Illinois 60626 USA

The structure and flexibility of the biologically important -spectrin amino terminal region was examined by the use of fluorescence and EPR spectroscopy. The region studied has been previously demonstrated to be essential for the -spectrin:-spectrin association of the tetramerization site. Appropriate spectroscopic probe moieties were coupled to this region in a recombinant fragment of human erythroid -spectrin. There was good agreement between the EPR and fluorescence techniques in most of this region. Mobility determinations indicated that a portion of the region was relatively immobilized. This is significant, since although predictive methods have indicated that this region should be -helical, previous experimental evidence obtained on smaller synthetic peptides had indicated that this region was disordered. Observed rigidity appears to be incompatible with such a disordered state, and has important ramifications for the flexibility of this molecule that is so integral to its role in stabilizing erythrocyte membranes.

Biophys J, July 2000, p. 526-535, Vol. 79, No. 1
© 2000 by the Biophysical Society   0006-3495/00/07/526/10  $2.00