Quasi-Racemic X-ray Structures of K27-Linked Ubiquitin Chains Prepared by Total Chemical Synthesis.

J Am Chem Soc

Tsinghua-Peking Center for Life Sciences, Ministry of Education Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology, Department of Chemistry, Tsinghua University, Beijing 100084, China.

Published: June 2016


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Article Abstract

Quasi-racemic crystallography has been used to determine the X-ray structures of K27-linked ubiquitin (Ub) chains prepared through total chemical synthesis. Crystal structures of K27-linked di- and tri-ubiquitins reveal that the isopeptide linkages are confined in a unique buried conformation, which provides the molecular basis for the distinctive function of K27 linkage compared to the other seven Ub chains. K27-linked di- and triUb were found to adopt different structural conformations in the crystals, one being symmetric whereas the other triangular. Furthermore, bioactivity experiments showed that the ovarian tumor family de-ubiquitinase 2 significantly favors K27-linked triUb than K27-linked diUb. K27-linked triUb represents the so-far largest chemically synthesized protein (228 amino acids) that has been crystallized to afford a high-resolution X-ray structure.

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