Complex energy landscape of a giant repeat protein.

TitleComplex energy landscape of a giant repeat protein.
Publication TypeJournal Article
Year of Publication2013
AuthorsTsytlonok, M., P. O. Craig, E. Sivertsson, D. Serquera, S. Perrett, R. B. Best, P. G. Wolynes, and L. S. Itzhaki
JournalStructure
Volume21
Issue11
Pagination1954-65
Date Published2013 Nov 5
ISSN1878-4186
Abstract

Here, we reveal a remarkable complexity in the unfolding of giant HEAT-repeat protein PR65/A, a molecular adaptor for the heterotrimeric PP2A phosphatases. The repeat array ruptures at multiple sites, leading to intermediate states with noncontiguous folded subdomains. There is a dominant sequence of unfolding, which reflects a nonuniform stability distribution across the repeat array and can be rationalized by theoretical models accounting for heterogeneous contact density in the folded structure. Unfolding of certain intermediates is, however, competitive, leading to parallel unfolding pathways. The low-stability, central repeats sample unfolded conformations under physiological conditions, suggesting how folding directs function: certain regions present rigid motifs for molecular recognition, whereas others have the flexibility with which to broaden the search area, as in the fly-casting mechanism. Partial unfolding of PR65/A also impacts catalysis by altering the proximity of bound catalytic subunit and substrate. Thus, the repeat array orchestrates the assembly and activity of PP2A.

DOI10.1016/j.str.2013.08.028
Alternate JournalStructure
PubMed ID24120762
Grant ListG1002329 / / Medical Research Council / United Kingdom
GM071862 / GM / NIGMS NIH HHS / United States
R01 GM44557 / GM / NIGMS NIH HHS / United States
Research group: