An Undecided Coiled Coil

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 15N 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.

Coiled-Coil Antagonism Regulates Activity of Venus Flytrap-Domain-Containing Sensor Kinases of the BvgS Family

“…By affecting the TM helices, modulation displaces the equilibrium in one direction or the other in a manner dependent on the initial state of the system, which is itself determined by the length of linker X. Such a mechanism of interconversion between two states of coiled coils triggered by external signals has been reported for Nek2, a eukaryotic kinase involved in cell cycle regulation ( 30 ). Other bacterial His kinases appear to function in a similar manner ( 31 ).…”

Assembly of the SLIP1–SLBP Complex on Histone mRNA Requires Heterodimerization and Sequential Binding of SLBP Followed by SLIP1

“…The spectra are characterized by a narrow chemical shift dispersion of ~1 p.p.m in the amide proton region over a pH range of 4–8 that is typical of either intrinsically disordered proteins(38) or coiled coils(39). NMR spectra of coiled coils such as leucine zippers are infamous for the lack of chemical shift dispersion in the amide proton region(40). To distinguish between these possibilities we collected 2D and 3D NOESY data and made 15 N relaxation measurements.…”

Growth Factor Identity Is Encoded by Discrete Coiled-Coil Rotamers in the EGFR Juxtamembrane Region

“…In fact, among dimeric, antiparallel polar coiled coil interfaces, the most common interfacial motif consists of polar residues at the core positions gd ’, dg’ , ae’ , and ea’ –precisely the arrangement seen in TGF-α-cluster 1 (Meier et al, 2010). Coiled coils stabilized by polar interactions have been observed in proteins whose function demands multiple interhelical interfaces (Croasdale et al, 2011) and short sequences that facilitate dimerization (Burkhard et al, 2000), two characteristics shared with the EGFR JM. Thus, the JM-A sequence, which possesses residues for both a hydrophobic helical interface and multiple salt bridging residues, uniquely allows the receptor to adopt multiple, distinct conformations.…”