Department of Biochemistry, University of Oulu, Finland.
J Mol Biol. 2011 Jun 10;409(3):291-7. doi: 10.1016/j.jmb.2011.03.070. Epub 2011 Apr 6.
The C-terminal amino acid sequence of a protein plays an important role in determining the endoplasmic reticulum (ER) localization of many soluble proteins that enter the secretory pathway. While it is known that the four amino acids found at the extreme C-terminus of the protein (e.g., KDEL) play a critical role in the interaction with the receptors that mediate retrograde transport back to the ER, other factors within the protein are less well known. Here we show that positions -5 and -6 play an important role in determining the ER localization of soluble proteins, with the amino acids at these positions playing an essential role in ER localization of the human protein disulfide isomerase family member, ERp18. Three other naturally occurring C-terminal motifs were also found that work efficiently in ER localization as six-amino-acid variants, but inefficiently as the four-amino-acid variant. Using bimolecular fluorescence complementation, we demonstrate that positions -5 and -6 from the C-terminus of the protein play an important role in the recognition of KDEL-like ER retrieval motifs, with the three different human KDEL receptors showing different specificities for changes at these positions for both inefficient and efficient ER localization four-amino-acid motifs.
蛋白质的 C 末端氨基酸序列在确定许多进入分泌途径的可溶性蛋白质的内质网 (ER) 定位中起着重要作用。虽然已知蛋白质的最末端的四个氨基酸（例如 KDEL）在与介导逆行运输回到 ER 的受体的相互作用中起着关键作用，但蛋白质内的其他因素则不太为人所知。在这里，我们表明位置-5 和-6 在确定可溶性蛋白质的 ER 定位中起着重要作用，这些位置的氨基酸对于人类蛋白质二硫键异构酶家族成员 ERp18 的 ER 定位起着至关重要的作用。还发现了另外三个天然存在的 C 末端基序，它们作为六氨基酸变体有效地用于 ER 定位，但作为四氨基酸变体则效率较低。使用双分子荧光互补，我们证明了蛋白质 C 末端的位置-5 和-6 在识别 KDEL 样 ER 回收基序中起着重要作用，三种不同的人类 KDEL 受体对这些位置的变化表现出不同的特异性，无论是对于低效和高效的 ER 定位四氨基酸基序。
