De novo metallopeptides are models for exploring native metallobiochemistry. The Pecoraro lab has been successful in designing parallel metal binding three stranded coiled coils (3SCC), both symmetric/ homotrimeric 3SCC (AAA) and asymmetric/heterotrimeric 3SCC (AAB). However, native metal binding sites are often asymmetric and found within antiparallel alpha helical bundles – a property we are not yet able to study within our 3SCC due to the inherent parallel self-assembly. Thus, designing specific antiparallel 3SCC (AABi) is a nontrivial yet attractive goal. Inverting the salt bridging residues of one TRI peptide, TRIi: G-LKALKEE4-G, and mixing stoichiometrically with a standard TRI peptide, G-LKALEEK4-G, in addition to a Pb(II)Cys3 binding site results in a successfully formed antiparallel heterotrimeric 3SCC, according to 207Pb NMR. Elongating the sequence to our GR peptides, GRi: G-LKALKEE5-G, containing two metal binding sites to obtain antiparallel 3SCC has been more elusive. A new inverted GR peptide has been synthesized considering both electrostatic interactions and leucine layer packing to best promote formation of the antiparallel heterotrimeric 3SCC. Spectroscopic characterization of the second His3 metal binding site in the GR peptides will also be explored via transition metal binding. It is hypothesized that the changes in the directionality of the 3SCC may affect not only the affinity but the ability for a second metal to bind to the His3 site. The results of these hypotheses and their implications will be presented.

Designing an antiparallel, asymmetric three-stranded coiled coil

251st National Meeting (2016)

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