Secondary literature sources for SecA_DEAD
The following references were automatically generated.
- Zimmer J, Li W, Rapoport TA
- A novel dimer interface and conformational changes revealed by an X-ray structure of B. subtilis SecA.
- J Mol Biol. 2006; 364: 259-65
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The SecA ATPase moves polypeptides post-translationally across the plasma membrane of eubacteria, but the mechanism of transport is still unclear. We describe the crystal structure of a novel dimeric form of Bacillus subtilis SecA. Dimerization of SecA occurs at the prominent groove formed by the nucleotide binding domain 2 (nbd2) and the preprotein cross-linking (ppx) domain. The dimer interface is very large, burying approximately 5400 A(2) of solvent accessible surface per monomer. Single cysteine disulfide cross-linking shows the presence of this novel SecA dimer in solution. In addition, other dimers also exist in solution, arguing that they all are in equilibrium with monomeric SecA and supporting the idea that the monomer may be the functional species. Dimerization of SecA causes an alpha-helix of one subunit to convert to a short beta-strand that participates in beta-sheet formation with strands in the other subunit. This conversion of secondary structure elements occurs close to the connection between the nbd1 and ppx domains, a potential site of interaction with translocation substrate. Comparing the different X-ray structures of B. subtilis SecA suggests that small changes in the nucleotide binding domains could be amplified via helix 1 of the helical scaffold domain (hsd) to generate larger movements of the domains involved in polypeptide binding.
- Nakatogawa H, Murakami A, Mori H, Ito K
- SecM facilitates translocase function of SecA by localizing its biosynthesis.
- Genes Dev. 2005; 19: 436-44
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"Arrest sequence" of Escherichia coli SecM interacts with the ribosomal exit tunnel and arrests its own translation elongation, which is released by cotranslational export of the nascent SecM chain. This property of SecM is essential for the basal and regulated expression of SecA. Here we report that SecM has an additional role of facilitating SecA activities. Systematic determinations of the SecA-abundance-protein export relationships of cells with different SecA contents revealed that SecA was less functional when SecM was absent from the upstream region of the secM-secA message, when SecM had the arrest-defective mutation, and also when SecM lacked the signal sequence. These results suggest that cotranslational targeting of nascent SecM to the translocon plays previously unrecognized roles of facilitating the formation of functional SecA molecules. Biosynthesis in the vicinity of the membrane and the Sec translocon will be beneficial for this multiconformation ATPase to adopt ready-to-function conformations.
- Fodje MN et al.
- Interplay between an AAA module and an integrin I domain may regulate the function of magnesium chelatase.
- J Mol Biol. 2001; 311: 111-22
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In chlorophyll biosynthesis, insertion of Mg(2+) into protoporphyrin IX is catalysed in an ATP-dependent reaction by a three-subunit (BchI, BchD and BchH) enzyme magnesium chelatase. In this work we present the three-dimensional structure of the ATP-binding subunit BchI. The structure has been solved by the multiple wavelength anomalous dispersion method and refined at 2.1 A resolution to the crystallographic R-factor of 22.2 % (R(free)=24.5 %). It belongs to the chaperone-like "ATPase associated with a variety of cellular activities" (AAA) family of ATPases, with a novel arrangement of domains: the C-terminal helical domain is located behind the nucleotide-binding site, while in other known AAA module structures it is located on the top. Examination by electron microscopy of BchI solutions in the presence of ATP demonstrated that BchI, like other AAA proteins, forms oligomeric ring structures. Analysis of the amino acid sequence of subunit BchD revealed an AAA module at the N-terminal portion of the sequence and an integrin I domain at the C terminus. An acidic, proline-rich region linking these two domains is suggested to contribute to the association of BchI and BchD by binding to a positively charged cleft at the surface of the nucleotide-binding domain of BchI. Analysis of the amino acid sequences of BchI and BchH revealed integrin I domain-binding sequence motifs. These are proposed to bind the integrin I domain of BchD during the functional cycle of magnesium chelatase, linking porphyrin metallation by BchH to ATP hydrolysis by BchI. An integrin I domain and an acidic and proline-rich region have been identified in subunit CobT of cobalt chelatase, clearly demonstrating its homology to BchD. These findings, for the first time, provide an insight into the subunit organisation of magnesium chelatase and the homologous colbalt chelatase.
- Mademidis A, Killmann H, Kraas W, Flechsler I, Jung G, Braun V
- ATP-dependent ferric hydroxamate transport system in Escherichia coli: periplasmic FhuD interacts with a periplasmic and with a transmembrane/cytoplasmic region of the integral membrane protein FhuB, as revealed by competitive peptide mapping.
- Mol Microbiol. 1997; 26: 1109-23
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The Escherichia coli iron transport system via ferrichrome belongs to the group of ATP-dependent transporters that are widely distributed in prokaryotes and eukaryotes. Transport across the cytoplasmic membrane is mediated by three proteins: FhuD in the periplasm, FhuB in the cytoplasmic membrane and FhuC (ATPase) associated with the inside of the cytoplasmic membrane. Interaction of FhuD with FhuB was studied in vitro with biotinylated synthetic 10 residue and 20-24 residue peptides of FhuB by determining the activity of beta-galactosidase linked to the peptides via streptavidin. Peptides identical in sequence to only one of the four periplasmic loops (loop 2), predicted by a transmembrane model of FhuB, and peptides representing a transmembrane segment and part of the adjacent cytoplasmic loop 7 of FhuB bound to FhuD. Decapeptides were transferred into the periplasm of cells through a FhuA deletion derivative that forms permanently open channels three times as large as the porins in the outer membrane. FhuB peptides that bound to FhuD inhibited ferrichrome transport, while peptides that did not bind to FhuD did not affect transport. These data led us to propose that the periplasmic FhuD interacts with a transmembrane region and the cytoplasmic segment 7 of FhuB. The transmembrane region may be part of a pore through which a portion of FhuD inserts into the cytoplasmic membrane during transport. The cytoplasmic segment 7 of FhuB contains the conserved amino acid sequence EAA...G (in FhuB DTA ...G) found in ABC transporters, which is predicted to interact with the cytoplasmic FhuC ATPase. Triggering of ATP hydrolysis by substrate-loaded FhuD may occur by physical interaction between FhuD and FhuC, which bind close to each other on loop 7. Although FhuB consists of two homologous halves, FhuB(N) and FhuB(C), the sites identified for FhuD-mediated ferrichrome transport are asymmetrically arranged.