title: Contribution of buried lysine residues to the oligomerization specificity and stability of the fos coiled coil.
abstract: Coiled coils comprise two or more helices characterized by a heptad repeat of amino acids denoted a through g. The buried a and d positions are usually occupied by hydrophobic residues. Fos dimerizes via a coiled coil (leucine zipper) with Jun family members to form the transcription factor AP-1. Fos homodimers are relatively unstable due to unfavorable interhelical electrostatic interactions within the Fos two-stranded coiled coil. The Fos coiled coil contains two polar position a Lys residues (Lys 16 and Lys 30 of Fos-p1, a peptide corresponding to the coiled-coil domain of v-Fos). Lys 16 and Lys 30 of Fos-p1 were replaced individually and together with the unnatural amino acid norleucine (2-aminohexanoic acid), which corresponds to a deletion of the Lys epsilon-amino group. The midpoint of thermal denaturation (T(m)) of Fos-p1 (10 microM) is 30 degrees C at pH 7. The Lys 16 --> Nle variant forms predominantly homodimers that are relatively unstable (T(m) = 46 degrees C). The Lys 30 --> Nle variant forms a stable homotetramer (T(m) = 60 degrees C). The Lys 16/Lys 30 --> Nle variant forms a very stable homotetramer (T(m) = 80 degrees C). The results show that (i) the effects of buried position a Lys residues on coiled-coil oligomerization are context dependent and (ii) electrostatic destabilization of the Fos homodimer can be mitigated by an oligomerization switch moderated by a single buried Lys residue.
authors.affiliation: Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523-1870, USA.
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Campbell
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Sholders
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Lumb
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002942:Circular Dichroism; D005456:Fluorescent Dyes; D016350:Leucine Zippers; D008239:Lysine; D046911:Macromolecular Substances; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry*; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence
chemical_list: D005456:Fluorescent Dyes; D046911:Macromolecular Substances; D010455:Peptides; D008239:Lysine