Homochiral and racemic MicroED structures of a peptide repeat from the ice-nucleation protein InaZ
The ice-nucleation protein InaZ from Pseudomonas syringae contains a large number of degenerate repeats that span more than a quarter of its sequence and include the segment GSTSTA.Ab initio structures of this repeat segment, resolved to 1.1 Å by microfocus X-ray crystallography and to 0.9 Å by the cryo-EM method MicroED, were determined from both racemic and homochiral crystals. The benefits of racemic protein crystals for structure determination by MicroED were evaluated and it was confirmed that the phase restriction introduced by crystal centrosymmetry increases the number of successful trials during the ab initio phasing of the electron diffraction data. Both homochiral and racemic GSTSTA form amyloid-like protofibrils with labile, corrugated antiparallel β-sheets that mate face to back. The racemic GSTSTA protofibril represents a new class of amyloid assembly in which all-left-handed sheets mate with their all-right-handed counterparts. This determination of racemic amyloid assemblies by MicroED reveals complex amyloid architectures and illustrates the racemic advantage in macromolecular crystallography, now with submicrometre-sized crystals.
- Research Organization:
- Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES); Howard Hughes Medical Institute; National Institutes of Health (NIH); National Institute of General Medical Sciences (NIGMS); National Science Foundation (NSF); Arnold and Mabel Beckman Foundation; Searle Scholars Program; Pew Charitable Trusts; QCB Collaboratory
- Grant/Contract Number:
- FC02-02ER63421; P41 GM103403; DMR 1548924; GM007185
- OSTI ID:
- 1617919
- Alternate ID(s):
- OSTI ID: 1502238
- Journal Information:
- IUCrJ, Journal Name: IUCrJ Vol. 6 Journal Issue: 2; ISSN 2052-2525
- Publisher:
- International Union of CrystallographyCopyright Statement
- Country of Publication:
- United Kingdom
- Language:
- English
Web of Science
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