Porcelli Ida, de Leeuw Erik, Wallis Russell, van den Brink-van der Laan Els, de Kruijff Ben, Wallace B A, Palmer Tracy, Berks Ben C
Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom.
Biochemistry. 2002 Nov 19;41(46):13690-7. doi: 10.1021/bi026142i.
Proteins bearing a signal peptide with a consensus twin-arginine motif are translocated via the Tat pathway, a multiprotein system consisting minimally of the integral inner membrane proteins TatA, TatB, and TatC. On a molar basis, TatA is the major pathway component. Here we show that TatA can be purified independently of the other Tat proteins as a 460 kDa homooligomeric complex. Homooligomer formation requires the amino-terminal membrane-anchoring domain of TatA. According to circular dichroism spectroscopy, approximately half of the TatA polypeptide forms alpha-helical secondary structure in both detergent solution and proteoliposomes. An expressed construct without the transmembrane segment is largely unstructured in aqueous solution but is able to insert into phospholipid monolayers and interacts with membrane bilayers. Protease accessibility experiments indicate that the extramembranous region of TatA is located at the cytoplasmic face of the cell membrane.
带有具有共有双精氨酸基序的信号肽的蛋白质通过Tat途径转运，Tat途径是一种多蛋白系统，至少由内膜整合蛋白TatA、TatB和TatC组成。按摩尔计算，TatA是主要的途径成分。在这里我们表明，TatA可以独立于其他Tat蛋白作为一个460 kDa的同聚体复合物被纯化。同聚体的形成需要TatA的氨基末端膜锚定结构域。根据圆二色光谱，大约一半的TatA多肽在去污剂溶液和蛋白脂质体中形成α-螺旋二级结构。一个没有跨膜片段的表达构建体在水溶液中基本无结构，但能够插入磷脂单层并与膜双层相互作用。蛋白酶可及性实验表明，TatA的膜外区域位于细胞膜的细胞质面。
