Domain dynamics of the Bacillus subtilis peripheral preprotein translocase subunit SecA

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The homodimeric SecA protein is the peripheral subunit of the preprotein translocase in bacteria. It promotes the preprotein translocation across the cytoplasmic membrane by nucleotide-modulated co-insertion and de-insertion into the integral domain of the translocase. SecA has two essential nucleotide binding sites (NBS): the high-affinity NBS-I resides in the amino-terminal domain of the protein and the low-affinity NBS-II is localized at 2/3 of the protein sequence. The nucleotide bound states of soluble SecA were studied by differential scanning calorimetry (DSC). Thermal unfolding reveals that the amino- and carboxy-terminal halves of SecA unfold independently with a transition midpoint of 49 and 40 degrees C, respectively. Binding of ADP to NBS-I increased the interaction between the two domains, whereas binding of AMPPNP does not influence this interaction. When ADP binds both NBS-I and NBS-II, SecA seems to have a more compact globular conformation, whereas binding of AMP-PNP seems to cause a more extended conformation. It is concluded that SecA is a two-domain protein and that the interaction between both domains is modulated by nucleotides. The compact ADP-bound conformation may resemble the membrane-de-inserted state of SecA, while the more extended ATP bound conformation may correspond to the membrane-inserted form of SecA.

Originele taal-2English
RedacteurenJE Ladbury, BZ Chowdhry
Plaats van productieCHICHESTER
Aantal pagina's13
ISBN van geprinte versie0-471-97781-0
StatusPublished - 1998
EvenementConference on the Applications of Calorimetry in the Biological Sciences -
Duur: 1-sep.-1996 → …


OtherConference on the Applications of Calorimetry in the Biological Sciences
Periode01/09/1996 → …

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