As molecular on-off switches, heterotrimeric G protein complexes, comprised of a Gα subunit and an obligate Gβγ dimer, transmit extracellular signals received by G protein-coupled receptors (GPCRs) to cytoplasmic targets that respond to biotic and abiotic stimuli. Signal transduction is modulated by phosphorylation of GPCRs and G protein complexes. In Arabidopsis thaliana, the Gα subunit AtGPA1 is phosphorylated by the receptor-like kinase (RLK) BRI1-associated Kinase 1 (BAK1), but the extent that other RLKs phosphorylates AtGPA1 is unknown. Twenty-two trans-phosphorylation sites on AtGPA1 are mapped by 12 RLKs hypothesized to act in the Arabidopsis G protein signaling pathway. Cis-phosphorylation sites are also identified on these RLKs, some newly shown to be dual specific kinases. Multiple sites are present in the core AtGPA1 functional units, including pSer52 and/or pThr53 of the conserved P-loop that directly binds nucleotide/phosphate, pThr164, and pSer175 from αE helix in the intramolecular domain interface for nucleotide exchange and GTP hydrolysis, and pThr193 and/or pThr194 in Switch I (SwI) that coordinates nucleotide exchange and protein partner binding. Several AtGPA1 S/T phosphorylation sites are potentially nucleotide-dependent phosphorylation patterns, such as Ser52/Thr53 in the P-loop and Thr193 and/or Thr194 in SwI.

中文翻译：

---

拟南芥异三聚体 G 蛋白 Gα 亚基 AtGPA1 的受体样激酶磷酸化。

作为分子开关，异三聚体 G 蛋白复合物由 Gα 亚基和专性 Gβγ 二聚体组成，将 G 蛋白偶联受体 (GPCR) 接收的细胞外信号传递到对生物和非生物刺激做出反应的细胞质靶标。信号转导受 GPCR 和 G 蛋白复合物的磷酸化调节。在拟南芥中，Gα 亚基 AtGPA1 被受体样激酶 (RLK) BRI1 相关激酶 1 (BAK1) 磷酸化，但其他 RLK 磷酸化 AtGPA1 的程度尚不清楚。AtGPA1 上的 22 个反式磷酸化位点由 12 个 RLK 定位，推测这些 RLK 在拟南芥 G 蛋白信号传导通路中发挥作用。这些 RLK 上还鉴定出了顺式磷酸化位点，其中一些新近显示为双特异性激酶。AtGPA1 核心功能单元中存在多个位点，包括直接结合核苷酸/磷酸盐的保守 P 环的 pSer52 和/或 pThr53、分子内结构域界面中 αE 螺旋的 pThr164 和 pSer175，用于核苷酸交换和 GTP 水解，以及Switch I (SwI) 中的 pThr193 和/或 pThr194 负责协调核苷酸交换和蛋白质伴侣结合。几个 AtGPA1 S/T 磷酸化位点可能是核苷酸依赖性磷酸化模式，例如 P 环中的 Ser52/Thr53 和 SwI 中的 Thr193 和/或 Thr194。