PROSITE documentation PDOC51884 [for PROSITE entry PS51884]

Chaplin domain profile

Streptomycetes differentiate by forming specialized spore-bearing aerial hyphae that grow into the air. In order to break surface tension streptomycetes have to coat their aerial hyphae in an extremely hydrophobic sheath that is absent from the vegetative hyphae growing in the aqueous phase. The hydrophobic sheath, which permits the aerial hyphae to escape surface tension and likely also prevents their desiccation in air, is made up of two families of proteins, the chaplins, for coelicolor hydrophobic aerial proteins, and the rodins. The chaplins are surface-active proteins that can be divided into two classes: the short chaplins and the long chaplins. The chaplins share a highly conserved, hydrophobic domain of ~40 amino acids, termed the chaplin domain, and all have an N-terminal Sec secretion signal. The short chaplins have one chaplin domain, whereas the long chaplins have two chaplin domains and a C-terminal 'sorting signal' that targets them for covalent attachment to the cell wall by sortase enzymes. The chaplins self-assemble via their chaplin domains into amyloid-like filaments on the surface of the aerial hyphae and spores [1,2,3].

There is no obvious pattern to the distribution of the hydrophobic residues, but there are three absolutely conserved GN motifs, spaced 12-13 residues apart, which may contribute to the structure of these domains. Secondary structure analysis predicts the chaplin domains to be rich in β-sheets, with the GN residues falling at the turns separating the individuals β-sheets [2].

The profile we developed covers the entire chaplin domain.