Biosynthesis of the various lipid species that compose cellular membranes and lipid droplets depends on the activity of multiple enzymes functioning in coordinated pathways. The flux of intermediates through lipid biosynthetic pathways is regulated to respond to nutritional and environmental demands placed on the cell necessitating that there be flexibility in pathway activity and organization. This flexibility can in part be achieved through the organization of enzymes into metabolon supercomplexes. However, the composition and organization of such supercomplexes remain unclear. Here, we identified protein–protein interactions between acyltransferases Sct1, Gpt2, Slc1, Dga1, and the Δ9 acyl-CoA desaturase Ole1 in Saccharomyces cerevisiae. We further determined that a subset of these acyltransferases interact with each other independent of Ole1. We show that truncated versions of Dga1 lacking the carboxyl-terminal 20 amino acid residues are nonfunctional and unable to bind Ole1. Furthermore, charged-to-alanine scanning mutagenesis revealed that a cluster of charged residues near the carboxyl terminus was required for the interaction with Ole1. Mutation of these charged residues disrupted the interaction between Dga1 and Ole1 but allowed Dga1 to retain catalytic activity and to induce lipid droplet formation. These data support the formation of a complex of acyltransferases involved in lipid biosynthesis that interacts with Ole1, the sole acyl-CoA desaturase in S. cerevisiae, that can channel unsaturated acyl chains toward phospholipid or triacylglycerol synthesis. This desaturasome complex may provide the architecture that allows for the necessary flux of de novo–synthesized unsaturated acyl-CoA to phospholipid or triacylglycerol synthesis as demanded by cellular requirements.

构成细胞膜和脂滴的各种脂质种类的生物合成取决于在协调途径中发挥作用的多种酶的活性。通过脂质生物合成途径的中间体流量受到调节，以响应细胞的营养和环境需求，从而需要途径活动和组织具有灵活性。这种灵活性部分可以通过将酶组织成代谢超级复合物来实现。然而，这种超级复合物的组成和组织仍不清楚。在这里，我们鉴定了酿酒酵母中酰基转移酶 Sct1、Gpt2、Slc1、Dga1 和 Δ9 酰基辅酶 A 去饱和酶 Ole1 之间的蛋白质-蛋白质相互作用。我们进一步确定这些酰基转移酶的一个子集独立于 Ole1 相互作用。我们发现，缺乏羧基末端 20 个氨基酸残基的 Dga1 的截短版本是无功能的，并且无法结合 Ole1。此外，带电至丙氨酸扫描诱变表明，与 Ole1 相互作用需要羧基末端附近的一簇带电残基。这些带电残基的突变破坏了 Dga1 和 Ole1 之间的相互作用，但允许 Dga1 保留催化活性并诱导脂滴形成。这些数据支持参与脂质生物合成的酰基转移酶复合物的形成，该复合物与酿酒酵母中唯一的酰基辅酶A去饱和酶Ole1相互作用，可以引导不饱和酰基链进行磷脂或三酰基甘油的合成。这种去饱和体复合物可以提供一种结构，允许从头合成的不饱和酰基辅酶A根据细胞需求向磷脂或三酰基甘油合成提供必要的通量。