SecA
| Eubacterial protein translocase subunit SecA | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| Symbol | SecA | ||||||||
| Pfam | PF07517 | ||||||||
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| Available protein structures: | |
|---|---|
| Pfam | structures |
| PDB | RCSB PDB; PDBe; PDBj |
| PDBsum | structure summary |
The SecA protein is a cell membrane associated subunit of the eubacterial Sec or Type II secretory pathway, a system which is responsible for the secretion of proteins through the cell membrane. Within this system SecA has the functional properties of an ATPase and is required to empower the movement of the protein substrate across the translocon channel.
The translocase system encompasses an array of proteins which are functionally centred on the translocon channel which mediates the export of proteins across the bacterial cytoplasmic membrane and the insertion of membrane proteins into it. Regardless of the chosen targeting route, preprotein eventually reach the cytoplasmic membrane and make contact with the translocase. This translocase consists out of the peripheral membrane ATPase SecA and the translocon membrane channel composed out of the proteins SecY, SecE, and SecG. Conformational changes within the SecA structure are the effect of its ATP-hydrolyzing behaviour and possibly lead to the stepwise export of the preprotein substrate through the SecYEG channel.
SecA is a complex protein which structure consists out of six characterized domains that can explain SecA’s capabilities to bind substrates and to move them. The following five domains seem to be present in all SecA proteins that have been structurally analyzed so far.
This amino acid domain is subdivided into the two nucleotide binding folds 1 and 2 (NBF1 and NBF2) where ATP is bound and hydrolyzed. The chemical energy from the phosphodiester bonds results in a conformational change which is transferred to other domains (especially the HWD and the PPXD domains) which consequently mechanically move the preprotein across the membrane. However, these conformational changes are partly regulated by other protomer domains described below.
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