Characterization of ordered aggregates of cerato-platanin and their involvement in fungus-host interactions.
BACKGROUND
The "cerato-platanin family" consists of fungal-secreted proteins that are involved in various stages of the host-fungus interaction and act as phytotoxins, elicitors of defense responses and allergens. Cerato-platanin (CP) is a moderately hydrophobic protein secreted and localized in the cell wall of Ceratocystis platani, the causal agent of a severe disease of Platanus. These properties make CP like the hydrophobins: these are self-assembling proteins that form a surface coating which is involved in the formation of aerial hyphae and in adherence to surfaces.


METHODS
CP aggregation was monitored by ThT, circular dichroism, and AFM. The eliciting activity of CP aggregates was assayed on leaves and cells.


RESULTS
The CP self-assembles forming amyloid-like aggregates via a nucleated growth mechanism which is joined up with a cleavage of the N-terminus. The ovoidal shape and the lack of a clear transition toward an all-beta structure distinguish these aggregates from typical amyloid fibrils. Moreover, CP aggregates interact with hydrophobic surfaces and enhance the hypersensitive response of Platanus.


CONCLUSIONS
CP forms "ordered aggregates" for which the soluble prefibrillar structures are the end point of the aggregation process, and do not evolve to insoluble fibrils. An involvement in host-microbe interaction is also suggested.
Pazzagli
Luigia
L
Department of Biochemical Sciences, Viale Morgagni 50-50134, University of Florence, Florence, Italy. luigia.pazzagli@unifi.it
Zoppi
Camilla
C
Carresi
Lara
L
Tiribilli
Bruno
B
Sbrana
Francesca
F
Schiff
Silvia
S
Pertinhez
Thelma A
TA
Scala
Aniello
A
Cappugi
Gianni
G
D000595:Amino Acid Sequence; D001203:Ascomycota / Q000737:chemistry / Q000502:physiology*; D002470:Cell Survival / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology; D054884:Host-Pathogen Interactions; D007700:Kinetics; D018625:Microscopy, Atomic Force; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology; D059828:Plant Cells; D010935:Plant Diseases / Q000382:microbiology*; D010944:Plants / Q000382:microbiology*; D011487:Protein Conformation; D017510:Protein Folding
C121379:Cerato-platanin protein, Ceratocystis fimbriata; D005656:Fungal Proteins; D010446:Peptide Fragments