NR AMQA
AU Wilson,D.; Valluzzi,R.; Kaplan,D.
TI Conformational transitions in model silk peptides
QU Biophysical Journal 2000 May; 78(5): 2690-701
PT journal article
AB Protein structural transitions and beta-sheet formation are a common problem both in vivo and in vitro and are of critical relevance in disparate areas such as protein processing and beta-amyloid and prion behavior. Silks provide a "databank" of well-characterized polymorphic sequences, acting as a window onto structural transitions. Peptides with conformationally polymorphic silk-like sequences, expected to exhibit an intractable beta-sheet form, were characterized using Fourier transform infrared spectroscopy, circular dichroism, and electron diffraction. Polymorphs resembling the silk I, silk II (beta-sheet), and silk III (threefold polyglycine II-like helix) crystal structures were identified for the peptide fibroin C (GAGAGS repetitive sequence). Two peptides based on silk amorphous sequences, fibroin A (GAGAGY) and fibroin V (GDVGGAGATGGS), crystallized as silk I under most conditions. Methanol treatment of fibroin A resulted in a gradual transition from silk I to silk II, with an intermediate state involving a high proportion of beta-turns. Attenuated total reflectance Fourier transform infrared spectroscopy has been used to observe conformational changes as the peptides adsorb from solution onto a hydrophobic surface. Fibroin C has a beta-strand structure in solution but adopts a silk I-like structure upon adsorption, which when dried on the ZnSe crystal contains silk III crystallites.
MH Amino Acid Sequence; Animal; Biophysics; Circular Dichroism; Fibroin/chemistry; Insect Proteins/*chemistry/ultrastructure; Microscopy, Electron; Molecular Sequence Data; Peptides/*chemistry; Protein Conformation; Protein Structure, Secondary; Silkworms; Solutions; Spectroscopy, Fourier Transform Infrared; Support, Non-U.S. Gov't; Support, U.S. Gov't, Non-P.H.S.
AD Department of Chemical Engineering and Biotechnology Center, Tufts University, Medford, Massachusetts 02155 USA.
SP englisch
PO USA