title: Selective formation of AAB- and ABC-type heterotrimeric alpha-helical coiled coils.
abstract: The alpha-helical coiled coils have a representative amino acid sequence of (abcdefg)(n) heptad repeats. We previously reported that two peptides named IZ-2A and IZ-2W formed an (IZ-2A)(2)/IZ-2W heterotrimer with an Ala-Ala-Trp interaction in the hydrophobic core. In this paper, we describe the selective formation of AAB- and ABC-type heterotrimers. To increase the selectivity of the AAB-type heterotrimeric formation, Lys residues at the f position were mutated to either an Ala or a Gln residue to form IZ-2A(fA) or IZ-2W(fQ). Separately, both IZ-2A(fA) and IZ-2W(fQ) have a random structure at pH 7 and 20 degrees C. However, together IZ-2A(fA) and IZ-2W(fQ) form a 2:1 complex with a thermal transition midpoint (Tm) of 48 degrees C. This procedure was applied to prepare the ABC-type heterotrimer, in which two sets of Ala-Ala-Trp interactions were designed in the hydrophobic core. Interhelical interaction between the e and g positions and the alpha-helical propensity of the amino acid at the f position were also considered in the design. The resultant three peptides selectively formed the ABC-type heterotrimer with a Tm of 51 degrees C. Other peptide combinations had random coil properties.
authors.affiliation: Department of Applied Biology, Kyoto Institute of Technology, Matugasaki, Sakyou-ku, Kyoto 606-8585, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Kiyokawa
authors.forename: Kenji
authors.initials: K
authors.lastname: Kanaori
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Tajima
authors.forename: Masataka
authors.initials: M
authors.lastname: Kawaguchi
authors.forename: Toshihisa
authors.initials: T
authors.lastname: Mizuno
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Oku
authors.forename: Toshiki
authors.initials: T
authors.lastname: Tanaka
mesh_terms: D000595:Amino Acid Sequence; D002942:Circular Dichroism; D019281:Dimerization; D010455:Peptides / Q000737:chemistry*; D011489:Protein Denaturation; D017433:Protein Structure, Secondary; D013050:Spectrometry, Fluorescence
chemical_list: D010455:Peptides