Effects of divalent metals on nanoscopic fiber formation and small molecule recognition of helical proteins

Susheel K. Gunasekar, Luona Anjia, Hiroshi Matsui, Jin K. Montclare

Research output: Contribution to journalArticlepeer-review

Abstract

Metal dependent protein-based assemblies derived from the cartilage oligomeric matrix protein (C) coiled-coil domain (His 6-C) and two variants with mutation at position 40 (His 6-T40A) and 44 (His 6-L44A) are explored. All proteins have an N-terminal hexahistidine tag (His 6) that interacts with divalent metal ions Zn(II) and Ni(II). Binding to Zn(II) confers enhanced helical structure and stability, while Ni(II) promotes aggregation. Surprisingly, His 6-L44A undergoes a conformational switch from unstructured to α-helix in the presence of Zn(II). Both His 6-C and His 6-T40A further assemble into discrete nanofibers that appear to be stabilized by Zn(II) in which the fiber formation is dictated by the α-helical content. Because Ni(II) promotes aggregation, the proteins visibly cluster, forming large fiber mats in the case of His 6-C and His 6-T40A or aggregated structures as observed for His 6-L44A. Due to the unique pentameric assembly of the proteins, recognition of a small molecule within the pore is assessed using curcumin as the guest molecule. In the presence of Zn(II), there is enhanced binding to curcumin, while the addition of Ni(II) causes a loss in binding. It is shown that metal binding serves as a trigger to control the conformation of the proteins, affecting the nanoscopic fibrous assemblies and small molecule recognition abilities.

Original languageEnglish (US)
Pages (from-to)2154-2159
Number of pages6
JournalAdvanced Functional Materials
Volume22
Issue number10
DOIs
StatePublished - May 23 2012

Keywords

  • coiled-coils
  • fibers
  • metals
  • self-assembly
  • small molecule recognition
  • stimuli-responsive materials

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

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