Simultaneous directed assembly of three distinct heterodimeric coiled coils

We describe simultaneous formation of three distinct heterodimeric coiled coils from a mixture of six different peptides. The choice among electrostatically viable complexes is governed by alignment of buried core residues, including a fundamentally new interaction that exploits urea-terminated side chains. Buried urea/urea contacts lead to extremely stable dimeric coiled coils, with T-m values between 63 and 79 degrees C. Core ureas can also form stable complexes with a variety of other polar groups, including guanidines, acids, and amides.