Hydrophobic core repacking in a coiled-coil dimer via phage display: insights into plasticity and specificity at a protein-protein interface.
The coiled-coil, which consists of two or more interwoven amphiphilic alpha-helices, is formed by sequences that have a characteristic heptad repeat (abcdefg) where a and d are hydrophobic residues. Most efforts to elucidate the origins of coiled-coil pairing selectivity have focused on electrostatic interactions among side chains that flank the core (positions e and g) and on polar side chains that occur occasionally at core positions. We have used phage display to explore another source of coiled-coil specificity: steric matching among nonpolar side chains in the core. We introduced a destabilizing Leu-->Ala mutation into the core of one helix in a known heterodimer and then screened a phage-based library of potential partner helices in search of compensating mutations. We identified a new heterodimer pair (30 residues/helix) that is comparable in stability to the GCN4-p1 homodimer (33 residues/helix). Furthermore, the Leu-->Ala mutant shows specificity for its phage-derived partner over the original partner despite their similar sequences. These results show that a phage-based approach can provide unique insights on coiled-coil pairing preferences that should facilitate both the analysis of natural sequences and the development of specific dimerization motifs that are orthogonal to one another.
Graduate Program in Biophysics, University of Wisconsin, Madison, Wisconsin 53706, USA.
Jonathan R
JR
Lai
John D
JD
Fisk
Bernard
B
Weisblum
Samuel H
SH
Gellman
D000409:Alanine / Q000737:chemistry; D000595:Amino Acid Sequence; D019281:Dimerization; D057927:Hydrophobic and Hydrophilic Interactions; D008969:Molecular Sequence Data; D019151:Peptide Library; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry*
D019151:Peptide Library; D011506:Proteins; D000409:Alanine