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Escherichia coli SecA shape and dimensions

Escherichia coli SecA shape and dimensions,10.1016/S0014-5793(98)01141-7,Febs Letters,Brian Shilton,Dmitri I. Svergun,Vladimir V. Volkov,Michel H. j.

Escherichia coli SecA shape and dimensions   (Citations: 21)
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SecA shape and conformational flexibility in solution were studied by small angle X-ray scattering. Dimeric SecA is a very elongated molecule, 15 nm long and 8 nm wide. SecA is therefore four times as long as the membrane is wide. The two globular protomers are distinctly separated and share limited surface of intermolecular contacts. ATP, ADP or adenylyl-imidodiphosphate (AMP-PNP) binding does not alter the SecA radius of gyration. A SecA mutant that catalyzes multiple rounds of ATP hydrolysis does not undergo conformational changes detectable by small angle X-ray scattering (SAXS). We conclude that SecA conformational alterations observed biochemically during nucleotide interaction are only small-scale and localized. The ramifications of these findings on SecA/SecYEG interaction are discussed.
Journal: Febs Letters - FEBS LETT , vol. 436, no. 2, pp. 277-282, 1998
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    • ...Additionally, medium and low resolution structures obtained by cryo-EM [93‐95], atomic force microscopy (AFM) [93], small angle X-ray scattering [96] and small angle neutron scattering [97] provide insight in SecA oligomerization and its conformational changes...

    Ilja KustersArnoldet al. SecA, a remarkable nanomachine

    • ...) and, in concentrated solutions, SecA is routinely isolated as a dime...

    Effrosyni Papanikouet al. Bacterial protein secretion through the translocase nanomachine

    • ...Derivatives that are devoid of CTD are fully functional in vivo and in vitro under our assay conditions and form dimeric proteins (Fig. 3A) [8,9,11,24]...

    Spyridoula Karamanouet al. Escherichia coli SecA truncated at its termini is functional and dimer...

    • ...Native SecA is isolated chromatographically as a stable dimer [42–45] that is seen by small-angle X-ray scattering (SAXS) to be elongated (815 nm) [45,46]...
    • ...The extended nature and dimensions of dimeric SecA, as determined from SAXS [45,46], SANS [51], electron microscopy [53] and crystallography [9,10] studies, make it difficult to envision how the enzyme deeply penetrates across the membrane [5,78–84] in a way that shields it from phospholipids [83,85]...
    • ...Nevertheless, no nucleotide-driven changes in the radius of gyration of SecA are detectable by SAXS analysis [45] and far-UV CD scan experiments failed to detect widespread changes in secondary structure [24,25,33]...
    • ...ADP release is the main rate-limiting step of SecA catalysis and hence SecAADP is a biochemically inert enzyme [25] that exhibits a compact conformation with local conformational changes in the SSD and Cdomains [24,57], while its overall shape is not changed [9,10,45]...
    • ...How the SecA dimer or monomer is accommodated in the membrane is difficult to envision considering the dimensions (158 nm) and shape of SecA dimer [9,10,45], the width of the membrane (5 nm) and the cavity, 1.62.5-nm wide and 2.2-nm deep, of the dimeric SecYEG [11,87]...

    Eleftheria Vrontouet al. Structure and function of SecA, the preprotein translocase nanomotor

    • ... The cavity is too small to enclose the entire SecA dimer, which measures about 150 × 80 × 80 Å (ref...

    Cécile Breytonet al. Three-dimensional structure of the bacterial protein-translocation com...

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