Fig. 2.

Non-canonical archaeal signal peptides of secretory proteins found in the medium fraction of Sulfolobus cells. a Signal peptides lacking positively charged residues in the N-domain. The predicted h-domain is underlined. b Class 3 signal peptides of substrate binding proteins. The signal peptidase cleavage recognition site is depicted in bold and underlined, with an arrow indicating the cleavage site. The consensus motifs of the signal cleavage site and of the region connecting the H-domain (underlined) are indicated. The H-domain is followed by a serine/threonine rich region that forms a potential glycosylation site