van Voorst F, van der Does C, Brunner J, Driessen A J, de Kruijff B
Department of Biochemistry of Membranes, Institute Biomembranes, Utrecht University, The Netherlands.
Biochemistry. 1998 Sep 1;37(35):12261-8. doi: 10.1021/bi9809021.
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.
大肠杆菌中的蛋白质转运由与SecYEG膜蛋白复合物结合的SecA ATP酶介导。SecA转运ATP酶活性以及蛋白质转运都依赖于带负电荷脂质的存在。通过使用带有酰基链连接的光可活化基团的磷脂，研究了结合在转运酶上的SecA的脂质可及性。发现结合到含有带负电荷脂质的脂质囊泡上的SecA很容易被光可活化磷脂标记。无论SecA的核苷酸结合形式如何，过量SecYEG复合物的存在都会导致脂质可及的SecA量显著减少。这些数据表明，与SecYEG结合的SecA在很大程度上被磷脂酰链屏蔽，并提示存在两个不同的膜结合SecA池，它们在脂质结合程度上有所不同。
