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Disordered Nanostructure in Huntingtin Interacting Protein K Acts as a Stabilizing Switch To Prevent Protein Aggregation.

Authors
  • Ghosh, Debasish Kumar1, 2
  • Roy, Ajit1
  • Ranjan, Akash1
  • 1 Computational and Functional Genomics Group , Centre for DNA Fingerprinting and Diagnostics , Nampally, Hyderabad 500001 , India. , (India)
  • 2 Graduate Studies , Manipal University , Manipal, Karnataka 576104 , India. , (India)
Type
Published Article
Journal
Biochemistry
Publisher
American Chemical Society
Publication Date
Apr 03, 2018
Volume
57
Issue
13
Pages
2009–2023
Identifiers
DOI: 10.1021/acs.biochem.7b00776
PMID: 29381348
Source
Medline
License
Unknown

Abstract

Protein misfolding due to mutation(s) and/or generation of unstable intermediate state(s) can be the cause of aberrant aggregations, leading to cellular degeneration. While molecular signatures like amyloidogenic regions cause aggregation, other features in proteins, like disorder and unique complexity regions, regulate and restrict such adhesive accumulation processes. Huntingtin interacting protein K (HYPK) is an aggregation-prone protein. Using various biophysical, microscopy, and computational techniques, we have deciphered how HYPK's N-terminal nanodisordered region plays a significant modulatory role in preventing its own aggregation and that of other proteins. HYPK's C-terminal hydrophobic regions lead to annular oligomerization and intermolecular charge interactions among the residues of low-complexity region (LCR) generate amorphous aggregates. The N-terminal disordered nanostructure loops toward the C-terminus, and a negative charge-rich patch in this region interacts with the LCR to shield LCR's positive charges. This interaction is required to prevent HYPK aggregation. Loss of this interaction causes partial unfolding of the structured C-terminus, resulting in HYPK's molten globule-like state and rapid annular oligomerization. The N-terminus also determines the specificity to mediate the differential bindings with aggregation-prone and wild type Huntingtin-exon1 proteins (Huntingtin97Q-exon1 and Huntingtin25Q-exon1). A sliding interaction of the specific N-terminal segment of HYPK along the extended polyglutamine region of Huntingtin-exon1 is responsible for HYPK's higher affinity for aggregation-prone Huntingtin than for its non-aggregating counterpart. Overall, our study provides evidence of the existence of disordered nanostructure in HYPK protein that mechanistically plays a decisive role in preventing both self and non-self protein aggregation.

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