Figure 1.

Alignment of related trigger sequences from two-stranded coiled coils. The coiled-coil trigger sequences from D. discoideum cortexillin I, yeast transcriptional activator GCN4, human kinesin, chicken gizzard smooth muscle myosin II heavy chain, and a tropomyosin-derived synthetic de novo coiled coil were identified based on their functional importance for coiled-coil formation reported in the literature. Additional sequences of known two-stranded coiled coils were localized by using the GCG Wisconsin sequence analysis software package. A sequence pattern search against swiss-prot with LEX(R, K)(L, V, I, A)X(R, E, K, D)XE and LEXE(L, V, I, A)X(R, E, K, D)X(R, K) has been applied, and zero mismatches were allowed. Human skeletal muscle tropomyosin β-chain, human tpr, and human Clip170 represent some selected examples. For each protein analyzed only one match with the derived sequence patterns was found. Heptad positions are indicated by lowercase letters. Residues that match the search pattern are in bold. Conserved potential interhelical attractive electrostatic interactions between ionizable side chains at positions e and g (residue i in chain 1 to residue i′+5 in chain 2; g to e′) are indicated in the derived consensus sequence. Moreover, with the exception of kinesin and tropomyosin all selected examples contain a possible i, i+8 intrahelical ionic interaction that exists in the N-terminal helix of the crystal structure of RNase A (24). Numbers refer to the amino acid positions within the native proteins. x, any residue; h, hydrophobic residue; c, charged residue.