Download MendeleyCryo-EM reveals ArnA contamination during purification of a ciliary protein complex.
Jiang, X., Kikkawa, M.(2026) Acta Crystallogr D Struct Biol 82: 404-410
- PubMed: 41984507 Search on PubMed
- DOI: https://doi.org/10.1107/S2059798326002846
- Primary Citation Related Structures:
21AK - PubMed Abstract:
Endogenous Escherichia coli proteins can co-purify with recombinant targets and dominate cryo-EM datasets, yet often escape detection during standard biochemical quality control. In parallel to the recent report by Caliseki and coworkers [Caliseki et al. (2025), Acta Cryst. D81, 545-557], we independently identified ArnA contamination while purifying a soluble, low-yield KIF17-IFT70 complex, ultimately obtaining a 3.23 Å resolution cryo-EM structure of ArnA rather than the intended target. Our results reinforce that ArnA enrichment reflects general features of His-tag affinity purification and can become particularly problematic in cryo-EM workflows when the intended target is low in yield or conformationally heterogeneous. By comparing biochemical behavior and cryo-EM outcomes, we outline why ArnA may evade SDS-PAGE and size-exclusion chromatography, and be underappreciated in routine mass spectrometry-based quality control, yet becomes structurally dominant in cryo-EM. These findings broaden the scope of the original study and highlight the need for early cryo-EM screening and improved contaminant awareness in structural biology.
- Department of Cell Biology and Anatomy, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan.
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