McFie Pamela J, Jin Youzhi, Banman Shanna L, Beauchamp Erwan, Berthiaume Luc G, Stone Scot J
Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada.
Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B4, Canada.
Biochim Biophys Acta. 2014 Sep;1841(9):1318-28. doi: 10.1016/j.bbalip.2014.06.004. Epub 2014 Jun 19.
Acyl CoA:diacylglycerol acyltransferase-2 (DGAT2) is an integral membrane protein that catalyzes the synthesis of triacylglycerol (TG). DGAT2 is present in the endoplasmic reticulum (ER) and also localizes to lipid droplets when cells are stimulated with oleate. Previous studies have shown that DGAT2 can interact with membranes and lipid droplets independently of its two transmembrane domains, suggesting the presence of an additional membrane binding domain. In order to identify additional membrane binding regions, we confirmed that DGAT2 has only two transmembrane domains and demonstrated that the loop connecting them is present in the ER lumen. Increasing the length of this short loop from 5 to 27 amino acids impaired the ability of DGAT2 to localize to lipid droplets. Using a mutagenesis approach, we were able to identify a stretch of amino acids that appears to have a role in binding DGAT2 to the ER membrane. Our results confirm that murine DGAT2 has only two transmembrane domains but also can interact with membranes via a previously unidentified helical domain containing its active site.
酰基辅酶A：二酰甘油酰基转移酶2（DGAT2）是一种催化三酰甘油（TG）合成的整合膜蛋白。DGAT2存在于内质网（ER）中，当细胞用油酸刺激时也定位于脂滴。先前的研究表明，DGAT2可以独立于其两个跨膜结构域与膜和脂滴相互作用，这表明存在一个额外的膜结合结构域。为了确定额外的膜结合区域，我们证实DGAT2只有两个跨膜结构域，并证明连接它们的环存在于内质网腔中。将这个短环的长度从5个氨基酸增加到27个氨基酸会损害DGAT2定位于脂滴的能力。使用诱变方法，我们能够鉴定出一段似乎在将DGAT2与内质网膜结合中起作用的氨基酸序列。我们的结果证实，小鼠DGAT2只有两个跨膜结构域，但也可以通过一个含有其活性位点的先前未鉴定的螺旋结构域与膜相互作用。
