FIGURE 1.

Membrane proteases implicated in the biogenesis of the cell envelope and extracellular appendages of the haloarchaeon Haloferax volcanii. Schematic representation of different protease families that participate in processes leading to the biogenesis of the cell envelope (cytoplasmic membrane, S-layer) and cell surface structures (archaellum, pili) in H. volcanii, and probably in other archaea. LonB is implicated in bacterioruberin biosynthesis and protein quality control. The signal peptidases Sec11a/b process the signal peptide of secreted and membrane proteins translocated through the Sec pathway. PibD cleaves preflagellins and prepilins, the protein components of the archaellum and pili. The rhomboid protease RhoII is involved in the N-glycosylation of the S-layer protein with a sulfoquinovose-containing oligosaccharide while archaeosortase ArtA mediates the proteolytic processing coupled-lipid modification of this glycoprotein facilitating its attachment to the archaeal cell surface.