CELL ADHESION, ADHESION, COILED COIL, TRIMERIC AUTOTRANSPORTER, CELL MEMBRANE, CELL OUTER MEMBRANE, MEMBRANE, PLASMID, VIRULENCE 3LT7 A TRANSITION FROM STRONG RIGHT-HANDED TO CANONICAL LEFT-HANDED SUPERCOILING IN A CONSERVED COILED COIL SEGMENT OF TRIMERIC AUTOTRANSPORTER ADHESINS - THE M3 MUTANT STRUCTURE