Conserved serine and histidine residues are critical for activity of the ER-type signal peptidase SipW of Bacillus subtilis.
Type I signal peptidases (SPases) are required for the removal of signal peptides from translocated proteins and, subsequently, release of the mature protein from the trans side of the membrane. Interestingly, prokaryotic (P-type) and endoplasmic reticular (ER-type) SPases are functionally equivalent, but structurally quite different, forming two distinct SPase families that share only few conserved residues. P-type SPases were, so far, exclusively identified in eubacteria and organelles, whereas ER-type SPases were found in the three kingdoms of life. Strikingly, the presence of ER-type SPases appears to be limited to sporulating Gram-positive eubacteria. The present studies were aimed at the identification of potential active site residues of the ER-type SPase SipW of Bacillus subtilis, which is required for processing of the spore-associated protein TasA. Conserved serine, histidine, and aspartic acid residues are critical for SipW activity, suggesting that the ER-type SPases employ a Ser-His-Asp catalytic triad or, alternatively, a Ser-His catalytic dyad. In contrast, the P-type SPases employ a Ser-Lys catalytic dyad (Paetzel, M., Dalbey, R. E., and Strynadka, N. C. J. (1998) Nature 396, 186-190). Notably, catalytic activity of SipW was not only essential for pre-TasA processing, but also for the incorporation of mature TasA into spores.
Tjalsma
H
H
Department of Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, Haren, The Netherlands.
Stover
A G
AG
Driks
A
A
Venema
G
G
Bron
S
S
van Dijl
J M
JM
D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry; D001224:Aspartic Acid / Q000737:chemistry; D001412:Bacillus subtilis / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D015153:Blotting, Western; D002384:Catalysis; D002458:Cell Fractionation; D017124:Conserved Sequence; D004591:Electrophoresis, Polyacrylamide Gel; D004721:Endoplasmic Reticulum / Q000737:chemistry*; D006639:Histidine / Q000737:chemistry*; D008565:Membrane Proteins; D008954:Models, Biological; D008969:Molecular Sequence Data; D010447:Peptide Hydrolases / Q000737:chemistry; D010957:Plasmids / Q000737:chemistry; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000737:chemistry*; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000378:metabolism*; D013170:Spores / Q000502:physiology
D019843:Archaeal Proteins; D001426:Bacterial Proteins; D008565:Membrane Proteins; C119938:TasA protein, Bacillus subtilis; D001224:Aspartic Acid; D012694:Serine; D006639:Histidine; D010447:Peptide Hydrolases; D012697:Serine Endopeptidases; C026515:type I signal peptidase