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2.A.6.4.3
Protein translocase subunit SecDF.  The 3-dimensional structure is known at 3.3 Å resolution (Tsukazaki et al. 2011).  SecDF serves several functions, such as stabilizing other Sec translocon components within the membrane, maintaining the transmembrane (TM) potential, and facilitating the ATP-independent stage of the translocation mechanism. SecDF also undergoes functionally important conformational changes that involve mainly its P1-head domain, and these changes are coupled with the proton motive force (Δpmf). Using all-atom molecular dynamics simulations combined with umbrella sampling, Ficici et al. 2017 studied the P1-head conformational change and how it is coupled to the pmf. They reported potentials of mean force along a root-mean-square-distance-based reaction coordinate obtained in the presence and absence of the TM electrical potential. Their results showed that the interaction of the P1 domain dipole moment with the TM electrical field lowers the free-energy barrier in the direction of the F-form to I-form transition, two conformations that vary by the relative positioning of the P1-head subdomain—the large periplasmic domain of TtSecDF—which is suggested to undergo a hinge motion (Ficici et al. 2017).

Accession Number:Q5SKE6
Protein Name:Protein translocase subunit SecDF
Length:735
Molecular Weight:79678.00
Species:Thermus thermophilus (strain HB8 / ATCC 27634 / DSM 579) [300852]
Number of TMSs:11
Location1 / Topology2 / Orientation3: Cell inner membrane1 / Multi-pass membrane protein2
Substrate proteins

Cross database links:

eggNOG: COG0341
HEGENOM: HOG000018636
Entrez Gene ID: 3168575   
Pfam: PF07549    PF02355   
KEGG: ttj:TTHA0697   

Gene Ontology

GO:0016021 C:integral to membrane
GO:0005622 C:intracellular
GO:0005886 C:plasma membrane
GO:0015450 F:P-P-bond-hydrolysis-driven protein transmembrane transporter activity
GO:0006886 P:intracellular protein transport

References (1)

[1] “Structure and function of a membrane component SecDF that enhances protein export.”  Tsukazaki T.et.al.   21562494
Structure:
2RRN   3AQO   3AQP     

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Predict TMSs (Predict number of transmembrane segments)
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FASTA formatted sequence
1:	MNRKNLTSLF LLGVFLLALL FVWKPWAPEE PKVRLGLDLK GGLRIVLEAD VENPTLDDLE 
61:	KARTVLENRI NALGVAEPLI QIQGQKRIVV ELPGLSQADQ DRALKLIGQR AVLEFRIVKE 
121:	GATGTTVAQI NQALRENPRL NREELEKDLI KPEDLGPPLL TGADLADARA VFDQFGRPQV 
181:	SLTFTPEGAK KFEEVTRQNI GKRLAIVLDG RVYTAPVIRQ AITGGQAVIE GLSSVEEASE 
241:	IALVLRSGSL PVPLKVAEIR AIGPTLGQDA IQAGIRSALI GTLAIFLLIF AYYGPHLGLV 
301:	ASLGLLYTSA LILGLLSGLG ATLTLPGIAG LVLTLGAAVD GNVLSFERIK EELRAGKKLR 
361:	QAIPEGFRHS TLTIMDVNIA HLLAAAALYQ YATGPVRGFA VILAIGVVAS VFSNLVFSRH 
421:	LLERLADRGE IRPPMWLVDP RFNFMGPARY VTAATLLLAA LAAGVVFAKG FNYSIDFTGG 
481:	TAYTLRAEPN VEVETLRRFL EEKGFPGKEA VITQVQAPTA AYREFLVKLP PLSDERRLEL 
541:	ERLFASELKA TVLASETVGP AIGEELRRNA VMAVLVGLGL ILLYVAFRFD WTFGVASILA 
601:	VAHDVAIVAG MYSLLGLEFS IPTIAALLTI VGYSINDSIV VSDRIRENQK LLRHLPYAEL 
661:	VNRSINQTLS RTVMTSLTTL LPILALLFLG GSVLRDFALA IFVGIFVGTY SSIYVVSALV 
721:	VAWKNRRKAQ EASKA