A novel class of secreted hydrophobic proteins is involved in aerial hyphae formation in Streptomyces coelicolor by forming amyloid-like fibrils.
Streptomycetes exhibit a complex morphological differentiation. After a submerged mycelium has been formed, filaments grow into the air to septate into spores. A class of eight hydrophobic secreted proteins, ChpA-H, was shown to be instrumental in the development of Streptomyces coelicolor. Mature forms of ChpD-H are up to 63 amino acids in length, and those of ChpA-C are larger (+/-225 amino acids). ChpA-C contain two domains similar to ChpD-H, as well as a cell-wall sorting signal. The chp genes were expressed in submerged mycelium (chpE and chpH) as well as in aerial hyphae (chpA-H). Formation of aerial hyphae was strongly affected in a strain in which six chp genes were deleted (DeltachpABCDEH). A mixture of ChpD-H purified from cell walls of aerial hyphae complemented the DeltachpABCDEH strain extracellularly, and it accelerated development in the wild-type strain. The protein mixture was highly surface active, and it self-assembled into amyloid-like fibrils at the water-air interface. The fibrils resembled those of a surface layer of aerial hyphae. We thus conclude that the amyloid-like fibrils of ChpD-H lower the water surface tension to allow aerial growth and cover aerial structures, rendering them hydrophobic. ChpA-C possibly bind ChpD-H to the cell wall.
Claessen
Dennis
D
Groningen Biomolecular Sciences and Biotechnology Institute (GBB), Department of Microbiology, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands.
Rink
Rick
R
de Jong
Wouter
W
Siebring
Jeroen
J
de Vreugd
Peter
P
Boersma
F G Hidde
FG
Dijkhuizen
Lubbert
L
Wosten
Han A B
HA
D000595:Amino Acid Sequence; D057927:Hydrophobic and Hydrophilic Interactions; D025301:Hyphae / Q000254:growth & development*; D008969:Molecular Sequence Data; D011506:Proteins / Q000378:metabolism*; D013302:Streptomyces / Q000254:growth & development*
D011506:Proteins