Table 1

Core components and associated domains of gram negative export and sorting systems

Export/Insertion System

Function

Core components

Domains

Localization1

Comments


General (Sec)

Translocation of unfolded proteins across the inner membrane

SecY

TIGR00967

Pfam00344

IM

Signal peptides cleaved by LspA tend to be shorter than those cleaved by LepB

SecE

TIGR00964

Pfam00584

IM

SecG

TIGR00810

Pfam03840

IM

Twin arginine (Tat)

Translocation of folded proteins across the inner membrane

TatA

TIGR01411

Pfam02416

IM

respiratory proteins that require cytoplasmic enzymes to covalently attachment metal cofactors (e.g. have iron sulfur, copper, molybdopterin) are expected substrates

TatB

TIGR01410

Pfam02416

IM

TatC

TIGR00945

Pfam00902

IM

Holin

Translocation of phage endolysin across the inner membrane

Holin

Numerous, but Genus-specific

IM

Encoded near endolysin in double-strand phage

Lol

Insertion of lipoproteins in the outer membrane

LolB

TIGR00548

Pfam03550

LP-OM

beta and gamma Proteobacteria also have LolA having TIGR00547 and pfam03548 domains

LolC

TIGR00548

Pfam03550

IM

LolD

TIGR00221

Cyt-IM assoc

LolE

TIGR02212

IM

Bam

Insertion of beta barrel proteins in the outer membrane

BamA

TIGR03303

OM

With the exception of proteins having large periplasmic domains, expect a genus-specific C-terminal sorting motif

BamB

TIGR03300

LP-OM

BamC

TIGR03302

LP-OM

BamD

pfam06804

LP-OM

BamE

Pfam04355

LP-OM


1Abbreviations - inner membrane (IM), outer membrane (OM), cytoplasmic, but associated with the inner membrane (Cyt-IM assoc), lipoprotein localized to the outer membrane (LP-OM)

Romine BMC Genomics 2011 12(Suppl 1):S1   doi:10.1186/1471-2164-12-S1-S1

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