Structural determinants for protein unfolding and translocation by the Hsp104 protein disaggregase

Journal Article · Fri Dec 22 00:00:00 EST 2017 · Bioscience Reports

DOI:https://doi.org/10.1042/BSR20171399· OSTI ID:1461438

Lee, Jungsoon ^[1]; Sung, Nuri ^[1]; Yeo, Lythou ^[1]; Chang, Changsoo ^[2]; Lee, Sukyeong ^[1]; Tsai, Francis T. F. ^[1]

---

1. Baylor College of Medicine, Houston, TX (United States)
2. Argonne National Lab. (ANL), Argonne, IL (United States)

Here, the ring-forming Hsp104 ATPase cooperates with Hsp70 and Hsp40 molecular chaperones to rescue stress-damaged proteins from both amorphous and amyloid-forming aggregates. The ability to do so relies upon pore loops present in the first ATP-binding domain (AAA-1; loop-1 and loop-2) and in the second ATP-binding domain (AAA-2; loop-3) of Hsp104, which face the protein translocating channel and couple ATP-driven changes in pore loop conformation to substrate translocation. A hallmark of loop-1 and loop-3 is an invariable and mutational sensitive aromatic amino acid (Tyr²⁵⁷ and Tyr⁶⁶²) involved in substrate binding. However, the role of conserved aliphatic residues (Lys²⁵⁶, Lys²⁵⁸, and Val⁶⁶³) flanking the pore loop tyrosines, and the function of loop-2 in protein disaggregation has not been investigated. Here we present the crystal structure of an N-terminal fragment of Saccharomyces cerevisiae Hsp104 exhibiting molecular interactions involving both AAA-1 pore loops, which resemble contacts with bound substrate. Corroborated by biochemical experiments and functional studies in yeast, we show that aliphatic residues flanking Tyr²⁵⁷ and Tyr⁶⁶² are equally important for substrate interaction, and abolish Hsp104 function when mutated to glycine. Unexpectedly, we find that loop-2 is sensitive to aspartate substitutions that impair Hsp104 function and abolish protein disaggregation when loop-2 is replaced by four aspartate residues. Our observations suggest that Hsp104 pore loops have non-overlapping functions in protein disaggregation and together coordinate substrate binding, unfolding, and translocation through the Hsp104 hexamer.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States)
• Sponsoring Organization: National Institutes of Health (NIH); USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 1461438
• Journal Information: Bioscience Reports, Vol. 37, Issue 6; ISSN 0144-8463
• Publisher: Portland Press - Biochemical Society
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES