Translocase-bound SecA is largely shielded from the phospholipid acyl chains.
Protein translocation in Escherichia coli is mediated by the SecA ATPase bound to the SecYEG membrane protein complex. SecA translocation ATPase activity as well as protein translocation is dependent on the presence of negatively charged lipids. By using a phospholipid with an acyl chain linked photoactivatable group, the lipid accessibility of SecA bound at the translocase was explored. SecA bound to lipid vesicles containing negatively charged lipids was found to be readily accessible for labeling by the photoactivatable phospholipid. The presence of an excess amount of SecYEG complex resulted in a remarkable reduction in the amount of lipid-accessible SecA irrespective of the nucleotide-bound form of SecA. These data demonstrate that the SecYEG-bound SecA is largely shielded from the phospholipid acyl chains and suggest the presence of two distinct pools of membrane-bound SecA that differ in the degree of lipid association.
Department of Biochemistry of Membranes, Institute Biomembranes, Utrecht University, The Netherlands. F.vanvoorst@chem.ruu.nl
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van Voorst
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van der Does
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Brunner
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Driessen
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de Kruijff
D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000378:metabolism*; D001389:Azirines / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D001692:Biological Transport; D005591:Chemical Fractionation; D029968:Escherichia coli Proteins; D007457:Iodine Radioisotopes; D008051:Lipid Bilayers / Q000378:metabolism; D008081:Liposomes / Q000378:metabolism; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000378:metabolism; D026901:Membrane Transport Proteins; D010713:Phosphatidylcholines / Q000378:metabolism; D010743:Phospholipids / Q000737:chemistry / Q000378:metabolism*; D011510:Proteolipids / Q000378:metabolism / Q000502:physiology; D000069816:SEC Translocation Channels; D000081416:SecA Proteins
D001389:Azirines; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D007457:Iodine Radioisotopes; D008051:Lipid Bilayers; D008081:Liposomes; D046911:Macromolecular Substances; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D010713:Phosphatidylcholines; D010743:Phospholipids; D011510:Proteolipids; D000069816:SEC Translocation Channels; C065493:SecE protein, E coli; C088616:SecG protein, E coli; C057841:SecY protein, E coli; C020485:proteoliposomes; C088423:1-palmitoyl-2-(decanedioyl mono-(2-iodo-4-(3-trifluoromethyl-3H-diazirin-3-yl)benzyl)ester)glycero-3-phosphocholine; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins