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PR01651

Identifier
SECGEXPORT  [View Relations]  [View Alignment]  
Accession
PR01651
No. of Motifs
4
Creation Date
23-DEC-2001
Title
Protein-export SecG membrane protein signature 
Database References
Literature References
1. BIEKER, K.L., PHILLIPS, G.J. AND SILHAVY, T.J. 
The sec and prl genes of Esherichia coli.
J.BIOENERG.BIOMEMBR. 22 291-310 (1990). 
 
2. FLOWER, A.M.
SecG function and phospholipid metabolism in Escherichia coli.
J.BACTERIOL. 183 2006-212 (2001).
 
3. BOST, S., SILVA, F., RUDAZ, C. AND BELIN, D.
Both transmembrane domains of SecG contribute to signal sequence recognition
by the Escherichia coli protein export machinery.
MOL.MICROBIOL. 38 575-587 (2000).
 
4. NAGAMORI, S., NISHIYAMA, K. AND TOKUDA, H.
Two SecG molecules present in a single protein translocation machinery are 
functional even after crosslinking.
J.BIOCHEM. 128 129-137 (2000).

Documentation
Secretion across the inner membrane in some Gram-negative bacteria occurs
via the preprotein translocase pathway. Proteins are produced in the 
cytoplasm as precursors, and require a chaperone subunit to direct them to 
the translocase component. [1]. From there, the mature proteins are either 
targeted to the outer membrane, or remain as periplasmic proteins [1]. The 
translocase protein subunits are encoded on the bacterial chromosome.
 
The translocase itself comprises 7 proteins, including a chaperone (SecB),
an ATPase (SecA), an integral membrane complex (SecY, SecE and SecG), and
two additional membrane proteins that promote the release of the mature 
peptide into the periplasm (SecD and SecF) [1]. SecG, a subunit of the major
translocase complex, is thought to stimulate translocation activity and 
enhance the insertion-deinsertion SecA cycle [2]. Deletion studies have
revealed that in the absence of SecG, and with an imbalance of membrane
phospholipids, translocation through the SecYEG complex cannot take place.
Thus, SecG is essential for the stabilisation/function of the SecYEG complex
in the bacterial membrane under stressful cell conditions [2].  
 
Using SecG mutants, it has been shown that SecG has two transmembrane (TM)
domains. Both of these contribute to the recognition of preprotein signal
sequences by the translocation complex [3]. The protein also undergoes
membrane topology inversion when coupled to the SecA cycle [4]. 
 
SECGEXPORT is a 4-element fingerprint that provides a signature for the 
protein-export SecG membrane proteins. The fingerprint was derived from an
initial alignment of 7 sequences: the motifs were drawn from conserved 
regions spanning the N-terminal portion of the alignment - motifs 1 and 4 
encode the TM domains, and motif 2 and 3 reside in the loop between them.
Two iterations on SPTR40_18f were required to reach convergence, at which
point a true set comprising 8 sequences was identified. A single partial
match was also found, Q98ME8, a protein-export membrane protein from
Rhizobium loti that fails to make a signficant match with motifs 2 and 3.
Summary Information
   8 codes involving  4 elements
0 codes involving 3 elements
1 codes involving 2 elements
Composite Feature Index
48888
30000
21001
1234
True Positives
Q9JRH8        Q9KU83        Q9PGJ6        SECG_ECOLI    
SECG_HAEIN SECG_PASMU SECG_PSEAE SECG_PSESY
True Positive Partials
Codes involving 2 elements
Q98ME8
Sequence Titles
Q9JRH8      HYPOTHETICAL PROTEIN SECG OR NMA0569 (PROTEIN-EXPORT MEMBRANE PROTEIN SECG) - Neisseria meningitidis (serogroup A), and Neisseria meningitidis (serogroup B). 
Q9KU83 PREPROTEIN TRANSLOCASE, SECG SUBUNIT - Vibrio cholerae.
Q9PGJ6 PROTEIN-EXPORT MEMBRANE PROTEIN - Xylella fastidiosa.
SECG_ECOLI Protein-export membrane protein secG (Preprotein translocase band 1 subunit) (P12) - Escherichia coli, and Escherichia coli O157:H7.
SECG_HAEIN Protein-export membrane protein secG - Haemophilus influenzae.
SECG_PASMU Protein-export membrane protein secG - Pasteurella multocida.
SECG_PSEAE Protein-export membrane protein secG - Pseudomonas aeruginosa.
SECG_PSESY Protein-export membrane protein secG - Pseudomonas syringae (pv. syringae).

Q98ME8 PROTEIN-EXPORT MEMBRANE PROTEIN - Rhizobium loti (Mesorhizobium loti).
Scan History
SPTR40_18f 2  100  NSINGLE    
Initial Motifs
Motif 1  width=21
Element Seqn Id St Int Rpt
TVLLVIYLLAAVAIIGLVLIQ Q9KU83 3 3 -
EALLVVFLIVAIGLVGLIMLQ SECG_ECOLI 3 3 -
KVVIVVHLLMALGLVGLILVQ SECG_PSEAE 4 4 -
QVLLFIYVVVAIALIGFILVQ SECG_HAEIN 3 3 -
TVVIVFHLLGALGVVALVLLQ SECG_PSESY 4 4 -
LLLNVIYVLVAIAMIVLILMQ Q9PGJ6 2 2 -
TLIWIVNIISALAVIVLVLLQ Q9JRH8 6 6 -

Motif 2 width=15
Element Seqn Id St Int Rpt
QQGKGADMGASFGAG Q9KU83 23 -1 -
QQGKGADMGASFGAG SECG_ECOLI 23 -1 -
QHGKGADAGASFGAG SECG_PSEAE 24 -1 -
QQGKGANAGASFGGG SECG_HAEIN 23 -1 -
QQGKGADAGASFGAG SECG_PSESY 24 -1 -
QRGTGAAAGSGFGAG Q9PGJ6 22 -1 -
QHGKGADAGATFGSG Q9JRH8 26 -1 -

Motif 3 width=17
Element Seqn Id St Int Rpt
ASNTVFGASGSGNFLTR Q9KU83 38 0 -
ASATLFGSSGSGNFMTR SECG_ECOLI 38 0 -
ASATVFGSQGSATFLSR SECG_PSEAE 39 0 -
ASGTMFGSAGAGNFLTR SECG_HAEIN 38 0 -
ASNTVFGGQGTSTFLSK SECG_PSESY 39 0 -
ASGTVFGSRGASNFLSK Q9PGJ6 37 0 -
SAQGVFGSAGNANFLSR Q9JRH8 43 2 -

Motif 4 width=23
Element Seqn Id St Int Rpt
RMTAIFATVFFVISLVLGNMSTH Q9KU83 54 -1 -
RMTALLATLFFIISLVLGNINSN SECG_ECOLI 54 -1 -
RITGILAAVFFLTSLGLAYFAKE SECG_PSEAE 55 -1 -
RTSAILATAFFVIALVLGNMNSH SECG_HAEIN 54 -1 -
KFTAILAACFFITSLGLGYFAKE SECG_PSESY 55 -1 -
KSTKWLAVVFFGISLFMAWYASR Q9PGJ6 53 -1 -
RSTAVAATFFFATCMAMVYIHTH Q9JRH8 59 -1 -
Final Motifs
Motif 1  width=21
Element Seqn Id St Int Rpt
TVLLVIYLLAAVAIIGLVLIQ Q9KU83 3 3 -
EALLVVFLIVAIGLVGLIMLQ SECG_ECOLI 3 3 -
KVVIVVHLLMALGLVGLILVQ SECG_PSEAE 4 4 -
QVLLFIYVVVAIALIGFILVQ SECG_HAEIN 3 3 -
QTLLLGYAIIAIVIVFLILIQ SECG_PASMU 3 3 -
TVVIVFHLLGALGVVALVLLQ SECG_PSESY 4 4 -
LLLNVIYVLVAIAMIVLILMQ Q9PGJ6 2 2 -
TLIWIVNIISALAVIVLVLLQ Q9JRH8 6 6 -

Motif 2 width=15
Element Seqn Id St Int Rpt
QQGKGADMGASFGAG Q9KU83 23 -1 -
QQGKGADMGASFGAG SECG_ECOLI 23 -1 -
QHGKGADAGASFGAG SECG_PSEAE 24 -1 -
QQGKGANAGASFGGG SECG_HAEIN 23 -1 -
QQGKGADAGASFGGG SECG_PASMU 23 -1 -
QQGKGADAGASFGAG SECG_PSESY 24 -1 -
QRGTGAAAGSGFGAG Q9PGJ6 22 -1 -
QHGKGADAGATFGSG Q9JRH8 26 -1 -

Motif 3 width=17
Element Seqn Id St Int Rpt
ASNTVFGASGSGNFLTR Q9KU83 38 0 -
ASATLFGSSGSGNFMTR SECG_ECOLI 38 0 -
ASATVFGSQGSATFLSR SECG_PSEAE 39 0 -
ASGTMFGSAGAGNFLTR SECG_HAEIN 38 0 -
ASGTIFGSVGSGNFLSK SECG_PASMU 38 0 -
ASNTVFGGQGTSTFLSK SECG_PSESY 39 0 -
ASGTVFGSRGASNFLSK Q9PGJ6 37 0 -
SAQGVFGSAGNANFLSR Q9JRH8 43 2 -

Motif 4 width=23
Element Seqn Id St Int Rpt
RMTAIFATVFFVISLVLGNMSTH Q9KU83 54 -1 -
RMTALLATLFFIISLVLGNINSN SECG_ECOLI 54 -1 -
RITGILAAVFFLTSLGLAYFAKE SECG_PSEAE 55 -1 -
RTSAILATAFFVIALVLGNMNSH SECG_HAEIN 54 -1 -
KMTALLATAFFVMSIVIGNVNSH SECG_PASMU 54 -1 -
KFTAILAACFFITSLGLGYFAKE SECG_PSESY 55 -1 -
KSTKWLAVVFFGISLFMAWYASR Q9PGJ6 53 -1 -
RSTAVAATFFFATCMAMVYIHTH Q9JRH8 59 -1 -