CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Instituto de Biología Molecular y Celular de Rosario (IBR), Universidad Nacional de Rosario, Argentina.
Plataforma Argentina de Biología Estructural y Metabolómica (PLABEM), Rosario, Argentina.
FEBS Lett. 2021 Jun;595(11):1525-1541. doi: 10.1002/1873-3468.14081. Epub 2021 Apr 16.
In the N-degron pathway of protein degradation of Escherichia coli, the N-recognin ClpS identifies substrates bearing N-terminal phenylalanine, tyrosine, tryptophan, or leucine and delivers them to the caseinolytic protease (Clp). Chloroplasts contain the Clp system, but whether chloroplastic ClpS1 adheres to the same constraints is unknown. Moreover, the structural underpinnings of substrate recognition are not completely defined. We show that ClpS1 recognizes canonical residues of the E. coli N-degron pathway. The residue in second position influences recognition (especially in N-terminal ends starting with leucine). N-terminal acetylation abrogates recognition. ClpF, a ClpS1-interacting partner, does not alter its specificity. Substrate binding provokes local remodeling of residues in the substrate-binding cavity of ClpS1. Our work strongly supports the existence of a chloroplastic N-degron pathway.
在大肠杆菌的 N 端肽段降解途径中，N 识别蛋白 ClpS 识别带有 N 端苯丙氨酸、酪氨酸、色氨酸或亮氨酸的底物，并将其递交给乳蛋白水解酶（Clp）。叶绿体含有 Clp 系统，但叶绿体 ClpS1 是否遵循相同的限制尚不清楚。此外，底物识别的结构基础尚未完全确定。我们表明 ClpS1 识别大肠杆菌 N 端肽段降解途径的典型残基。第二位残基影响识别（尤其是以亮氨酸开头的 N 端末端）。N 端乙酰化会破坏识别。ClpF，ClpS1 的相互作用伙伴，不会改变其特异性。底物结合会引起 ClpS1 底物结合腔中残基的局部重塑。我们的工作强烈支持叶绿体 N 端肽段降解途径的存在。
