title: De novo design of a pentameric coiled-coil: decoding the motif for tetramer versus pentamer formation in water-soluble phospholamban.
abstract: Water-soluble phospholamban (WSPLB) is a designed, water-soluble analogue of the pentameric membrane protein phospholamban (PLB), which contains the same core and interhelical residues as PLB, with only the solvent-exposed positions mutated. WSPLB contains the same secondary and quaternary structure as PLB. The hydrophobic cores of PLB and WSPLB contain Leu and Ile at the a- and d-positions of a heptad repeat (abcdefg) from residues 31-52, while residues 21-30 are rich in polar amino acids at these positions. While the full-length WSPLB forms pentamers in solution, truncated peptides lacking residues 21-30 are largely tetrameric. Thus, truncation of residues 1-20 promotes a switch from pentamer to tetramer formation. Here, the motifs for WSPLB pentamerization were elucidated by characterizing a series of peptides, which were progressively truncated in this polar 'switch' region. When fully present, the 'switch' region promotes pentamer formation in WSPLB, by destabilizing a more stable tetrameric species which exists in its absence. We find that the burial of hydrogen bonding residues from 21 to 30 drives WSPLB from a tetramer to a pentamer, with direct implications for coiled-coil design.
authors.affiliation: Department of Biochemistry and Molecular Biophysics, Johnson Foundation, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Slovic
authors.forename: J D
authors.initials: JD
authors.lastname: Lear
authors.forename: W F
authors.initials: WF
authors.lastname: DeGrado
mesh_terms: D020816:Amino Acid Motifs; D002135:Calcium-Binding Proteins / Q000737:chemistry*; D002942:Circular Dichroism; D008958:Models, Molecular; D010446:Peptide Fragments / Q000737:chemistry; D011489:Protein Denaturation; D015202:Protein Engineering; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012995:Solubility; D014867:Water; D000099211:Phospholamban
chemical_list: D002135:Calcium-Binding Proteins; D010446:Peptide Fragments; D014867:Water; D000099211:Phospholamban