Taxonomic distribution of proteins containing SecA_DEAD domains

The tree below includes only several representative species and genera. The complete taxonomic breakdown of all proteins containing SecA_DEAD domains can be accessed here. Click the counts or percentage values to display the corresponding proteins.

Nucleotide control of interdomain interactions in the conformationalreaction cycle of SecA.

Hunt JF, Weinkauf S, Henry L, Fak JJ, McNicholas P, Oliver DB, Deisenhofer J
Science. 2002; 297: 2018-26

The SecA adenosine triphosphatase (ATPase) mediates extrusion of the aminotermini of secreted proteins from the eubacterial cytosol based on cyclesof reversible binding to the SecYEG translocon. We have determined thecrystal structure of SecA with and without magnesium-adenosine diphosphatebound to the high-affinity ATPase site at 3.0 and 2.7 angstrom resolution,respectively. Candidate sites for preprotein binding are located on asurface containing the SecA epitopes exposed to the periplasm upon bindingto SecYEG and are thus positioned to deliver preprotein to SecYEG.Comparisons with structurally related ATPases, including superfamily I andII ATP-dependent helicases, suggest that the interaction geometry of thetandem motor domains in SecA is modulated by nucleotide binding, which isshown by fluorescence anisotropy experiments to reverse an endothermicdomain-dissociation reaction hypothesized to gate binding to SecYEG.

Amino-terminal region of SecA is involved in the function of SecG forprotein translocation into Escherichia coli membrane vesicles.

Mori H, Sugiyama H, Yamanaka M, Sato K, Tagaya M, Mizushima S
J Biochem. 1998; 124: 122-9

Protein translocation across the cytoplasmic membrane of Escherichia coliis accomplished by concerted actions of the translocation ATPase SecA andthe membrane-embedded SecE/Y/G complex. SecA interacts with preproteinsand undergoes ATP-driven cycles of membrane insertion-deinsertion. Toaddress how SecA interacts functionally with other components in thetranslocation machinery, we characterized a SecA mutant lackingamino-terminal 8 amino acid residues (SecA N-8). Although the absence ofthe 8 residues did not grossly affect the interaction of SecA with apreprotein, ATP, or phospholipids, nor did it affect the intrinsic ATPaseactivity, it gave differential effects on the translocation of differentpreproteins. It also affected the translocation ATPase activity, theability of membrane insertion, and the topology inversion of SecG coupledwith the membrane insertion-deinsertion of SecA. Most noteworthy, SecA N-8was pronouncedly defective in the translocation of proton motiveforce-dependent preproteins, in which SecG might have a role. We proposethat the amino-terminal region of SecA is important for the functionalinteraction with SecG.

SecA protein hydrolyzes ATP and is an essential component of the proteintranslocation ATPase of Escherichia coli.

Lill R, Cunningham K, Brundage LA, Ito K, Oliver D, Wickner W
EMBO J. 1989; 8: 961-6

Bacterial protein export requires two forms of energy input, ATP and themembrane electrochemical potential. Using an in vitro reactionreconstituted with purified soluble and peripheral membrane components, wecan now directly measure the translocation-coupled hydrolysis of ATP. Thistranslocation ATPase requires inner membrane vesicles, SecA protein andtranslocation-competent proOmpA. The stimulatory activity of membranevesicles can be blocked by either antibody to the SecY protein or bypreparing the membranes from a secY-thermosensitive strain which had beenincubated at the non-permissive temperature in vivo. The SecA proteinitself has more than one ATP binding site. 8-azido-ATP inactivates SecAfor proOmpA translocation and for translocation ATPase, yet does notinhibit a low level of ATP hydrolysis inherent in the isolated SecAprotein. These data show that the SecA protein has a central role incoupling the hydrolysis of ATP to the transfer of pre-secretory proteinsacross the membrane.