Title: The apo-structure of the leucine sensor Sestrin2 is still elusive

Abstract

Sestrin2 is a GATOR2-interacting protein that directly binds leucine and is required for the inhibition of mTORC1 under leucine deprivation, indicating that it is a leucine sensor for the mTORC1 pathway. We recently reported the structure of Sestrin2 in complex with leucine [Protein Data Bank (PDB) ID, 5DJ4] and demonstrated that mutations in the leucine-binding pocket that alter the affinity of Sestrin2 for leucine result in a corresponding change in the leucine sensitivity of mTORC1 in cells. A lower resolution structure of human Sestrin2 (PDB ID, 5CUF), which was crystallized in the absence of exogenous leucine, showed Sestrin2 to be in a nearly identical conformation as the leucine-bound structure. On the basis of this observation, it has been argued that leucine binding does not affect the conformation of Sestrin2 and that Sestrin2 may not be a sensor for leucine. We show that simple analysis of the reported “apo”-Sestrin2 structure reveals the clear presence of prominent, unmodeled electron density in the leucine-binding pocket that exactly accommodates the leucine observed in the higher resolution structure. Refining the reported apo-structure with leucine eliminated the large F_obs-F_calc difference density at this position and improved the working and free R factors of the model. Consistentmore » with this result, our own structure of Sestrin2 crystallized in the absence of exogenous leucine also contained electron density that is best explained by leucine. Thus, the structure of apo-Sestrin2 remains elusive.« less

Authors:

Saxton, Robert A. ^[1]; Knockenhauer, Kevin E. ^[2]; Schwartz, Thomas U. ^[2]; Sabatini, David M. ^[1]

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+ Show Author Affiliations

1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Whitehead Inst. for Biomedical Research, Cambridge, MA (United States); Howard Hughes Medical Inst., Cambridge, MA (United States); Koch Inst. for Integrative Cancer Research, Cambridge, MA (United States); Broad Inst., Cambridge, MA (United States)
2. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)

Publication Date:

Tue Sep 20 00:00:00 EDT 2016

Research Org.:

Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS)

Sponsoring Org.:

USDOE Office of Science (SC); National Institute of General Medical Sciences (NIGMS); National Institutes of Health (NIH); Office of Research Infrastructure Programs (ORIP); USDOD

OSTI Identifier:

1328786

Grant/Contract Number:  

S10 RR029205; AC02-06CH11357; R01CA103866; AI47389; W81XWH-07-0448

Resource Type:

Accepted Manuscript

Journal Name:

Science Signaling

Additional Journal Information:

Journal Volume: 9; Journal Issue: 446; Journal ID: ISSN 1945-0877

Publisher:

AAAS

Country of Publication:

United States

Language:

ENGLISH

Subject:

59 BASIC BIOLOGICAL SCIENCES