Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1177777 | Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics | 2012 | 12 Pages |
Fiber-forming proteins and peptides are being scrutinized as a promising source of building blocks for new nanomaterials. Arabinogalactan-like (AGL) proteins expressed at the symbiotic interface between plant roots and arbuscular mycorrhizal fungi have novel sequences, hypothesized to form polyproline II (PPII) helix structures. The functional nature of these proteins is unknown but they may form structures for the establishment and maintenance of fungal hyphae. Here we show that recombinant AGL1 (rAGL1) and recombinant AGL3 (rAGL3) are extended proteins based upon secondary structural characteristics determined by electronic circular dichroism (CD) spectroscopy and can self-assemble into fibers and microtubes as observed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). CD spectroscopy results of synthetic peptides based on repeat regions in AGL1, AGL2 and AGL3 suggest that the synthetic peptides contain significant amounts of extended PPII helices and that these structures are influenced by ionic strength and, at least in one case, by concentration. Point mutations of a single residue of the repeat region of AGL3 resulted in altered secondary structures. Self-assembly of these repeats was observed by means of AFM and optical microscopy. Peptide (APADGK)6 forms structures with similar morphology to rAGL1 suggesting that these repeats are crucial for the morphology of rAGL1 fibers. These novel self-assembling sequences may find applications as precursors for bioinspired nanomaterials.
► Recombinant proteins based on genes from a symbiotic fungus self-assemble into fibers. ► Repetitive proline- and glycine-rich peptides with novel sequences inspired by fungal proteins. ► Synthetic repetitive peptides also form fibers and are affected by ionic conditions. ► Secondary structure of proteins and peptides is predominantly polyproline II. ► Secondary structure of synthetic repetitive peptides is sensitive to single residue mutations.