Kumar C M Santosh, Mai Aisha M, Mande Shekhar C, Lund Peter A
Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Birmingham, UK.
National Centre for Cell Science, Pune, India.
Commun Biol. 2025 Apr 8;8(1):555. doi: 10.1038/s42003-025-07927-x.
E. coli chaperonin GroEL forms nano-cages for protein folding. Although the chaperonin-mediated protein folding mechanism is well understood, the role of the conserved glycine and methionine-rich carboxy-terminal residues remains unclear. Bacteria with multiple chaperonins always retain at least one paralogue having the gly-met-rich C-terminus, indicating an essential conserved function. Here, we observed a stronger selection pressure on the paralogues with gly-met-rich C-termini, consistent with their ancestral functional importance. E. coli GroEL variants having mutations in their C-termini failed to functionally replace GroEL, suggesting the functional significance of the gly-met-rich C-termini. Further, our structural modelling and normal mode analysis showed that the C-terminal region shuttles between two cavity-specific conformations that correlate with the client-protein-binding apical domains, supporting C-termini's role in client protein encapsulation. Therefore, employing phylogenetic, genetic, and structural tools, we demonstrate that the gly-met-rich C-termini are functionally significant in chaperonin-mediated protein folding function. Owing to the pathogenic roles of the chaperonins having non-canonical C-termini, future investigations on the client protein selectivity will enable understanding the disease-specific client protein folding pathways and treatment options.
大肠杆菌伴侣蛋白GroEL形成用于蛋白质折叠的纳米笼。尽管伴侣蛋白介导的蛋白质折叠机制已得到充分理解，但富含保守甘氨酸和甲硫氨酸的羧基末端残基的作用仍不清楚。具有多种伴侣蛋白的细菌总是保留至少一种具有富含甘氨酸-甲硫氨酸的C末端的旁系同源物，这表明其具有重要的保守功能。在这里，我们观察到对具有富含甘氨酸-甲硫氨酸的C末端的旁系同源物有更强的选择压力，这与其祖先的功能重要性一致。在其C末端具有突变的大肠杆菌GroEL变体无法在功能上替代GroEL，这表明富含甘氨酸-甲硫氨酸的C末端具有功能重要性。此外，我们的结构建模和正常模式分析表明，C末端区域在两种与客户蛋白结合的顶端结构域相关的腔特异性构象之间穿梭，支持C末端在客户蛋白封装中的作用。因此，通过系统发育、遗传和结构工具，我们证明富含甘氨酸-甲硫氨酸的C末端在伴侣蛋白介导的蛋白质折叠功能中具有功能重要性。由于具有非典型C末端的伴侣蛋白的致病作用，未来对客户蛋白选择性的研究将有助于理解疾病特异性的客户蛋白折叠途径和治疗选择。
