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Shifting transition states in the unfolding of a large ankyrin repeat protein.

ABSTRACT: The 33-amino-acid ankyrin motif comprises a beta-turn followed by two anti-parallel alpha-helices and a loop and tandem arrays of the motif pack in a linear fashion to produce elongated structures characterized by short-range interactions. In this article we use site-directed mutagenesis to investigate the kinetic unfolding mechanism of D34, a 426-residue, 12-ankyrin repeat fragment of the protein ankyrinR. The data are consistent with a model in which the N-terminal half of the protein unfolds first by unraveling progressively from the start of the polypeptide chain to form an intermediate; in the next step, the C-terminal half of the protein unfolds via two pathways whose transition states have either the early or the late C-terminal ankyrin repeats folded. We conclude that the two halves of the protein unfold by different mechanisms because the N-terminal moiety folds and unfolds in the context of a folded C-terminal moiety, which therefore acts as a "seed" and confers a unique directionality on the process, whereas the C-terminal moiety folds and unfolds in the context of an unfolded N-terminal moiety and therefore behaves like a single-domain ankyrin repeat protein, having a high degree of symmetry and consequently more than one unfolding pathway accessible to it.

SUBMITTER: Werbeck ND

PROVIDER: S-EPMC2481366 | biostudies-literature | 2008 Jul

REPOSITORIES: biostudies-literature

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Shifting transition states in the unfolding of a large ankyrin repeat protein.

Werbeck Nicolas D ND Rowling Pamela J E PJ Chellamuthu Vasuki R VR Itzhaki Laura S LS

Proceedings of the National Academy of Sciences of the United States of America 20080716 29

The 33-amino-acid ankyrin motif comprises a beta-turn followed by two anti-parallel alpha-helices and a loop and tandem arrays of the motif pack in a linear fashion to produce elongated structures characterized by short-range interactions. In this article we use site-directed mutagenesis to investigate the kinetic unfolding mechanism of D34, a 426-residue, 12-ankyrin repeat fragment of the protein ankyrinR. The data are consistent with a model in which the N-terminal half of the protein unfolds ...[more]

PMID: 18632570

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Project description:Background:Left ventricular assist devices (LVADs) have revolutionized and improved the care of the sickest heart failure (HF) patients, and it is imperative that they receive appropriate ventricular unloading. Assessing this critical parameter with current methodologies (labs, imaging) is usually suboptimal in this patient population. Hence it is imperative to elucidate the molecular underpinnings involved in ventricular unloading. We have previously identified the cytoskeletal protein ?II spectrin as an essential nodal protein involved in post-translational targeting and ?II spectrin protein levels are significantly altered in multiple forms of human and animal HF. We therefore hypothesized that the ?II spectrin pathway would play a critical role in LVAD remodeling. Methods:Human heart failure samples were obtained from patients undergoing heart transplantation. Wild type (WT) mice and our previously validated ?II spectrin conditional knock out (?II cKO) mice were used for animal experiments. Transaortic constriction (TAC) was performed on WT mice. Protein expression was assessed via immunoblots, and protein interactions were assessed with co-immunoprecipitation. Transcriptome analysis was performed using isolated whole hearts from control adult WT mice (n = 3) compared to ?II cKO spectrin mice (n = 3). Results:We report that hearts from mice selectively lacking ?II spectrin expression in cardiomyocytes displayed altered transcriptional regulation of cardiac ankyrin repeat protein (CARP). Notably, CARP protein expression is increased after TAC. Additionally, our findings illustrate that prior to LVAD support, CARP levels are elevated in HF patients compared to normal healthy controls. Further, for the first time in a LVAD population, we show that elevated CARP levels in HF patients return to normal following LVAD support. Conclusion:Our findings illustrate that CARP is a dynamic molecule that responds to reduced afterload and stress, and has the potential to serve as a prognostic biomarker to assess for an adequate response to LVAD therapy.

Dataset Information

Shifting transition states in the unfolding of a large ankyrin repeat protein.

Publications

Shifting transition states in the unfolding of a large ankyrin repeat protein.

Similar Datasets

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