Journal
ADVANCED FUNCTIONAL MATERIALS
Volume 22, Issue 10, Pages 2154-2159Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adfm.201101627
Keywords
self-assembly; fibers; metals; stimuli-responsive materials; coiled-coils; small molecule recognition
Categories
Funding
- AFOSR [FA-9550-07-1-0060, FA-9550-08-1-0266]
- ARO [W911NF-11-1-0449]
- NSF MRSEC [DMR-0820341]
- U.S. Department of Energy, Office of Basic Energy Sciences [DE-AC02-98CH10886]
- U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering [DE-FG-02-01ER45935]
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Metal dependent protein-based assemblies derived from the cartilage oligomeric matrix protein (C) coiled-coil domain (His6-C) and two variants with mutation at position 40 (His6-T40A) and 44 (His6-L44A) are explored. All proteins have an N-terminal hexahistidine tag (His6) 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, His6-L44A undergoes a conformational switch from unstructured to a-helix in the presence of Zn(II). Both His6-C and His6-T40A further assemble into discrete nanofibers that appear to be stabilized by Zn(II) in which the fiber formation is dictated by the a-helical content. Because Ni(II) promotes aggregation, the proteins visibly cluster, forming large fiber mats in the case of His6-C and His6-T40A or aggregated structures as observed for His6-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.
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