Domain dynamics of the Bacillus subtilis peripheral preprotein translocase subunit SecA
| Autor: | Driessen, A.J.M., Ladbury, JE, Chowdhry, BZ |
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| Přispěvatelé: | Molecular Microbiology |
| Jazyk: | angličtina |
| Rok vydání: | 1998 |
| Předmět: | |
| Zdroj: | BIOCALORIMETRY, 253-265 STARTPAGE=253;ENDPAGE=265;TITLE=BIOCALORIMETRY |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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