title: N@a and N@d: Oligomer and Partner Specification by Asparagine in Coiled-Coil Interfaces.
abstract: The α-helical coiled coil is one of the best-studied protein-protein interaction motifs. As a result, sequence-to-structure relationships are available for the prediction of natural coiled-coil sequences and the de novo design of new ones. However, coiled coils adopt a wide range of oligomeric states and topologies, and our understanding of the specification of these and the discrimination between them remains incomplete. Gaps in our knowledge assume more importance as coiled coils are used increasingly to construct biomimetic systems of higher complexity; for this, coiled-coil components need to be robust, orthogonal, and transferable between contexts. Here, we explore how the polar side chain asparagine (Asn, N) is tolerated within otherwise hydrophobic helix-helix interfaces of coiled coils. The long-held view is that Asn placed at certain sites of the coiled-coil sequence repeat selects one oligomer state over others, which is rationalized by the ability of the side chain to make hydrogen bonds, or interactions with chelated ions within the coiled-coil interior of the favored state. We test this with experiments on de novo peptide sequences traditionally considered as directing parallel dimers and trimers, and more widely through bioinformatics analysis of natural coiled-coil sequences and structures. We find that when located centrally, rather than near the termini of such coiled-coil sequences, Asn does exert the anticipated oligomer-specifying influence. However, outside of these bounds, Asn is observed less frequently in the natural sequences, and the synthetic peptides are hyperthermostable and lose oligomer-state specificity. These findings highlight that not all regions of coiled-coil repeat sequences are equivalent, and that care is needed when designing coiled-coil interfaces.
authors.affiliation: School of Chemistry, University of Bristol , Cantock's Close, Bristol BS8 1TS, United Kingdom.
authors.forename: Jordan M
authors.initials: JM
authors.lastname: Fletcher
authors.affiliation: School of Chemistry, University of Bristol , Cantock's Close, Bristol BS8 1TS, United Kingdom.
authors.forename: Gail J
authors.initials: GJ
authors.lastname: Bartlett
authors.affiliation: School of Chemistry, University of Bristol , Cantock's Close, Bristol BS8 1TS, United Kingdom.
authors.forename: Aimee L
authors.initials: AL
authors.lastname: Boyle
authors.affiliation: School of Chemistry, University of Bristol , Cantock's Close, Bristol BS8 1TS, United Kingdom.
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Danon
authors.affiliation: School of Chemistry, University of Bristol , Cantock's Close, Bristol BS8 1TS, United Kingdom.
authors.forename: Laura E
authors.initials: LE
authors.lastname: Rush
authors.affiliation: Department of Protein Evolution, Max Planck Institute for Developmental Biology , 72076 Tübingen, Germany.
authors.forename: Andrei N
authors.initials: AN
authors.lastname: Lupas
authors.affiliation: School of Chemistry, University of Bristol , Cantock's Close, Bristol BS8 1TS, United Kingdom.|School of Biochemistry, University of Bristol , Medical Sciences Building, University Walk, Bristol BS8 1TD, United Kingdom.|BrisSynBio, University of Bristol , Life Science Building, Tyndall Avenue, Bristol BS8 1TQ, United Kingdom.
authors.forename: Derek N
authors.identifier: 0000-0002-0394-3202
authors.initials: DN
authors.lastname: Woolfson
mesh_terms: D000595:Amino Acid Sequence; D001216:Asparagine / Q000737:chemistry*; D001704:Biopolymers / Q000737:chemistry*; D002942:Circular Dichroism; D057927:Hydrophobic and Hydrophilic Interactions; D011485:Protein Binding; D011506:Proteins / Q000737:chemistry
chemical_list: D001704:Biopolymers; D011506:Proteins; D001216:Asparagine