DOI: 10.1101/473116Nov 19, 2018Paper

Homochiral and racemic MicroED structures of a peptide from the ice nucleation protein InaZ

BioRxiv : the Preprint Server for Biology
Chih-Te ZeeJose A Rodriguez

Abstract

The ice nucleation protein InaZ of Pseudomonas syringae contains a large number of degenerate repeats that span more than a quarter of its sequence and include the segment GSTSTA. We determine ab initio structures of this repeat segment, resolved to 1.1A by microfocus x-ray crystallography and 0.9A by the cryoEM method MicroED, from both racemic and homochiral crystals. We evaluate the benefits of racemic protein crystals for structure determination by MicroED and confirm that phase restriction introduced by crystal centrosymmetry increases the number of successful trials during ab initio phasing of electron diffraction data. Both homochiral and racemic GSTSTA form amyloid-like protofibrils with labile, corrugated antiparallel beta 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. Our determination of racemic amyloid assemblies by MicroED reveals complex amyloid architectures and illustrates the racemic advantage in macromolecular crystallography, now with sub-micron sized crystals.

Related Concepts

Amyloid
Biomaterials
Clinical Trials
Crystallography
Peptides
Microbiology Procedure
Crystallography, X-Ray
Structure of Left Hand
Cytochrome-c Oxidase Deficiency
Pseudomonas syringae

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