Structural basis of substrate recognition and thermal protection by a small heat shock protein

• Published in: Nature communications Vol. 12; no. 1; p. 3007
• Main Authors: Yu, Chuanyang, Leung, Stephen King Pong, Zhang, Wenxin, Lai, Louis Tung Faat, Chan, Ying Ki, Wong, Man Chit, Benlekbir, Samir, Cui, Yong, Jiang, Liwen, Lau, Wilson Chun Yu
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 21.05.2021; Nature Publishing Group; Nature Portfolio
• Subjects: 101/28; 631/449/2661; 631/45/470/1981; 631/45/535/1258/1259; Agglomeration; Crystallin; D-Xylulose 5-phosphate; Dimers; Electron microscopy; Heat shock proteins; Heat stress; Heat tolerance; Humanities and Social Sciences; multidisciplinary; Proteins; Recognition; Science; Science (multidisciplinary); Small heat shock proteins; Structural members; Substrates; Thermal protection; Xylulose
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-021-23338-y

Small heat shock proteins (sHsps) bind unfolding proteins, thereby playing a pivotal role in the maintenance of proteostasis in virtually all living organisms. Structural elucidation of sHsp-substrate complexes has been hampered by the transient and heterogeneous nature of their interactions, and the precise mechanisms underlying substrate recognition, promiscuity, and chaperone activity of sHsps remain unclear. Here we show the formation of a stable complex between Arabidopsis thaliana plastid sHsp, Hsp21, and its natural substrate 1-deoxy-D-xylulose 5-phosphate synthase (DXPS) under heat stress, and report cryo-electron microscopy structures of Hsp21, DXPS and Hsp21-DXPS complex at near-atomic resolution. Monomeric Hsp21 binds across the dimer interface of DXPS and engages in multivalent interactions by recognizing highly dynamic structural elements in DXPS. Hsp21 partly unfolds its central α-crystallin domain to facilitate binding of DXPS, which preserves a native-like structure. This mode of interaction suggests a mechanism of sHsps anti-aggregation activity towards a broad range of substrates. Structural insights into the small heat shock proteins (sHsps) complexes with their substrates are sparse. Here, cryo-EM structure of a plastid sHsp, Hsp21, in complex with a bona fide substrate 1-deoxy-D-xylulose 5-phosphate synthase (DXPS), suggests the anti-aggregation mechanism employed by sHsps.