TABLE 1.

Extracellular proteins of B. subtilis 168 with export signals^a

Protein	Function or similarity	Export signalb	SPase	Retention signalc	Mediumd
AbnA	Arabinan-endo-1,5-α-l-arabinase	KRe	SPase I	−	LB
AmyE	α-Amylase	Sec	SPase I	−	LB, PS,
AprE	Serine alkaline protease (subtilisin E)	Sec	SPase I	−	LB, PS
BglC	Endo-1,4-β-glucanase, cellulase	KRe	SPase I	−	LB
BglS	Endo-β-1,3-1,4 glucanase	KRe	SPase I	−	LB, PS
Bpr	Bacillopeptidase F	Sec	SPase I	−	LB, PS
Csn	Chitosanase	Sec	SPase I	−	LB, MG
Epr	Minor extracellular serine protease	Sec	SPase I	−	LB
Ggt	γ-Glutamyltranspeptidase	Sec	SPase I	−	LB
GlpQ	Glycerophosphoryl diester	Sec	SPase I	−	PS
HtrA	Serine protease	TM	Unknownf	−	LB
LipA	Lipase	RRe	SPase I	−	LB
LytD	N-Acetylglucosaminidase (major autolysin)	KRe	SPase I	CWB	LB, PS
MntA	Manganese-binding protein	Lipo	LspA	Lipid	LB
Mpr	Extracellular metalloprotease	Sec	SPase I	−	LB
NprE	Extracellular neutral metalloprotease	Sec	SPase I	−	LB, PS
OppA	Oligopeptide-binding protein	Lipo/KRe	LspA	Lipid	LB, PS
PbpA	Penicillin-binding protein 2A	TM	Unknownf	−	LB
PbpX	Penicillin-binding protein	RRe	SPase I	−	LB
Pel	Pectate lyase	Sec	SPase I	−	LB, PS, MG
PelB	Pectate lyase	Sec	SPase I	−	LB
PenP	β-Lactamase precursor	Sec	SPase I	−	LB, MG
PhoA	Alkaline phosphatase A	Sec	SPase I	−	PS
PhoB	Alkaline phosphatase III	Sec	SPase I	−	PS
PhoD	Phosphodiesterase/alkaline phosphatase D	RR	SPase I	−	PS
PstS	Phosphate-binding protein	Lipo	LspA	Lipid	PS
TasA	Antimicrobial spore component	Sec	SipWg	−	LB, MG
Vpr	Extracellular serine protease	Sec	SPase I	−	LB, PS,
WapA	Cell wall-associated protein precursor	RRe	SPase I	CWB	LB, PS, MG
WprA	Cell wall-associated protein precursor	RRe	SPase I	CWBh	LB, PS, MG
XynA	Endo-1,4-β-xylanase	Sec	SPase I	−	LB, PS
XynD	Endo-1,4-β-xylanase	Lipo	LspA	Lipid	LB, PS, MG
YbdN	Unknown	Sec	SPase I	−	LB
YbxI	Similar to β-lactamase	Sec	SPase I	−	LB
YcdH	Zinc-binding protein	Lipo	LspA	Lipid	PS
YclQ	Ferrichrome-binding protein	Lipo	LspA	Lipid	LB, PS, MG
YdhF	Similar to unknown proteins from B. subtilis	Lipo/RRe	LspA	Lipid	PS
YdhT	Mannan endo-1,4-β-mannosidase	Sec	SPase I	−	MC
YfkN	2′,3′-Cyclic-nucleotide 2′-phosphodiesterase	RRe	SPase I	TM	LB, PS
YfIE	Similar to anion-binding protein	TM	SPase I	−	MG
YfmC	Ferrichrome-binding protein	Lipo	LspA	Lipid	LB
YfnI	Probable transmembrane glycoprotein	TM	SipT/SipVi	−	LB, PS, MG
YhcR	5′-Nucleotidase	RRe	SPase I	TM	LB
YlqB	Unknown	Sec	SPase I	−	LB, PS, MG
YncM	Similar to unknown proteins from B. subtilis	Sec	SPase I	−	LB, PS, MG
YnfF	Endo-xylanase	Sec	SPase I	−	LB, PS
YoaW	Unknown	Sec	SPase I	−	LB
YocH	Cell wall-binding protein	Sec	SPase I	CWBj	LB
YolA	Unknown	KRe	SPase I	−	LB
YqiX	Amino acid-binding protein	Lipo	LspA	Lipid	LB
YqxI	Unknown	Sec	SPase I	−	LB
YrpD	Similar to unknown proteins from B. subtilis	Sec	SPase I	−	LB, PS
YrpE	Similar to unknown proteins	Lipo	LspA	Lipid	PS
YuaB	Unknown	Sec	SPase I	−	LB
YurI	RNase	Sec	SPase I	−	LB
YvcE	Cell wall-binding protein	Sec	SPase I	CWB10	LB
YvgO	Unknown	Sec	SPase I	−	LB
YvpA	Pectate lyase	Sec	SPase I	−	LB
YwaD	Aminopeptidase	Sec	SPase I	−	LB
YweA	Similar to unknown proteins from B. subtilis	Sec	SPase I	−	LB, PS
YwoF	Unknown	Sec	SPase I	−	LB, PS
YwtD	γ-dl-Glutamyl hydrolase	Sec	SPase I	CWB10	LB, PS, MG
YwtF	Transcriptional regulator	Sec	SPase I	−	LB
YxaLk	Similar to serine/threonine protein kinase	Sec	SPase I	−	LB, PS, MG
YxiA	Arabinan-endo-1,5-α-l-arabinase	Sec	SPase I	−	LB
YxkC	Unknown	Sec	SPase I	−	LB, PS, MG

^aAll listed proteins were identified by 2D PAGE and subsequent MALDI-TOF mass spectrometry and/or N-terminal amino acid sequencing as described by Hirose et al. (46), Jongbloed et al. (51, 52), and Antelmann et al. (3-6). Putative signal peptides. SPase I or SPase II cleavage sites, transmembrane domains, and cell wall-binding domains were predicted as described by Tjalsma et al. (129) and Jongbloed et al. (51).

^bIdentified transient export signals are Sec-type signal peptides (Sec), twin-arginine signal peptides (RR/KR), lipoprotein signal peptides (Lipo), and transmembrane domains (TM).

^cIdentified retention signals present in the mature part of the protein after processing by specific SPases are lipid modifications (Lipid), transmembrane domains (TM), and cell wall-binding domains (CWB). −, absence of known retention signals.

^dProteins found in the extracellular proteomes of cells were grown in LB broth (rich medium) (4, 5, 6, 51), phosphate starvation medium (PS) (3, 5, 52), or minimal medium with glucose (M_G) or cellobiose (M_C) (46).

^eDespite the presence of putative RR/KR-type signal peptides, release of AbnA, BglC, BglS, LipA, LytD, OppA, PbpX, WapA, WprA, YdhF, YfkN, YhcR, and YolA into the growth medium is not Tat dependent (51).

^fAs pre-PbpA and pre-HtrA lack putative SPase I cleavage sites, it is unknown which protease is responsible for their cleavage and subsequent release into the medium (4, 5).

^gpre-TasA processing and release of mature TasA into the medium is strictly dependent on the ER-type SPase SipW (126, 131).

^hWprA is known to be a major cell wall protein (6, 68), but it lacks a typical cell wall-binding motif.

ⁱRelease of the C-terminal part of YfnI into the medium was shown to be dependent on the presence of SipT or SipV (5).

^jDespite the presence of putative cell wall-binding domains, YocH, YvcE, and YwtD are not detected in the cell wall proteome of B. subtilis 168 (6).

^kThe protein YxaL was previously annotated as YxaK (5).