title: An undecided coiled coil: the leucine zipper of Nek2 kinase exhibits atypical conformational exchange dynamics.
abstract: Leucine zippers are oligomerization domains used in a wide range of proteins. Their structure is based on a highly conserved heptad repeat sequence in which two key positions are occupied by leucines. The leucine zipper of the cell cycle-regulated Nek2 kinase is important for its dimerization and activation. However, the sequence of this leucine zipper is most unusual in that leucines occupy only one of the two hydrophobic positions. The other position, depending on the register of the heptad repeat, is occupied by either acidic or basic residues. Using NMR spectroscopy, we show that this leucine zipper exists in two conformations of almost equal population that exchange with a rate of 17 s(-1). We propose that the two conformations correspond to the two possible registers of the heptad repeat. This hypothesis is supported by a cysteine mutant that locks the protein in one of the two conformations. NMR spectra of this mutant showed the predicted 2-fold reduction of peaks in the (15)N HSQC spectrum and the complete removal of cross peaks in exchange spectra. It is possible that interconversion of these two conformations may be triggered by external signals in a manner similar to that proposed recently for the microtubule binding domain of dynein and the HAMP domain. As a result, the leucine zipper of Nek2 kinase is the first example where the frameshift of coiled-coil heptad repeats has been directly observed experimentally.
authors.affiliation: Department of Biochemistry, University of Leicester, Leicester LE1 9HN, United Kingdom.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Croasdale
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Ivins
authors.forename: Fred
authors.initials: F
authors.lastname: Muskett
authors.forename: Tina
authors.initials: T
authors.lastname: Daviter
authors.forename: David J
authors.initials: DJ
authors.lastname: Scott
authors.forename: Tara
authors.initials: T
authors.lastname: Hardy
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Smerdon
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Fry
authors.forename: Mark
authors.initials: M
authors.lastname: Pfuhl
mesh_terms: D001483:Base Sequence; D002942:Circular Dichroism; D017931:DNA Primers; D006801:Humans; D016350:Leucine Zippers; D016297:Mutagenesis, Site-Directed; D000072379:NIMA-Related Kinases; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000235:genetics; D014461:Ultracentrifugation
chemical_list: D017931:DNA Primers; C089441:NEK2 protein, human; D000072379:NIMA-Related Kinases; D017346:Protein Serine-Threonine Kinases