Contribution of Buried Lysine Residues to the Oligomerization Specificity and Stability of the Fos Coiled Coil

• Published in: Biochemistry (Easton) 2002-04, Vol.41 (15), p.4866-4871
• Main Authors: Campbell, Kathleen M, Sholders, Aaron J, Lumb, Kevin J
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Binding Sites; Circular Dichroism; Fluorescent Dyes; Leucine Zippers; Lysine; Macromolecular Substances; Models, Molecular; Molecular Sequence Data; Peptides - chemistry; Protein Conformation; Spectrometry, Fluorescence
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi0159276

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 ε-amino group. The midpoint of thermal denaturation (T m) of Fos-p1 (10 μM) is 30 °C at pH 7. The Lys 16 → Nle variant forms predominantly homodimers that are relatively unstable (T m = 46 °C). The Lys 30 → Nle variant forms a stable homotetramer (T m = 60 °C). The Lys 16/Lys 30 → Nle variant forms a very stable homotetramer (T m = 80 °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.