In article <9110011939.AA12054 at genbank.bio.net> MICROB at PLUMCS11.BITNET (Marek Tchorzewski) writes: > Have you heard about "Leucine zipper" or "Bilateral hydrophobic zipper". Scientific American April 1991 page 54. Tom Schneider National Cancer Institute Laboratory of Mathematical Biology Frederick, Maryland 21702-1201 toms at ncifcrf.gov