HELIX-HELIX PACKING IN A MEMBRANE-LIKE ENVIRONMENT

The unique ability of the glycophorin A transmembrane helix to dimeriz e in SDS has previously been exploited in studies of the sequence spec ificity of helix-helix packing in a micellar environment. Here, we hav e made different insertion mutants in the critical helix-helix interfa ce segment, and find that efficient dimerization can be mediated by a wider range of sequence motifs than suggested by the earlier studies. We also show that certain mutants that are unable to dimerize can neve rtheless form relatively high amounts of tetramers, and that specific tetramerization can be induced by duplication of the critical interfac e motif on the lipid-exposed side of the transmembrane helix. (C) 1997 Academic Press Limited.