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Publication Abstract from PubMed

Pulsed electron paramagnetic resonance experiments can measure individual distances between two spin-labeled side chains in proteins in the range of approximately 1.5-8 nm. However, the flexibility of traditional spin-labeled side chains leads to diffuse spin density loci and thus distance distributions with relatively broad peaks, thereby complicating the interpretation of protein conformational states. Here we analyzed the spin-labeled V1 side chain, which is internally anchored and hence less flexible. Crystal structures of V1-labeled T4 lysozyme constructs carrying the V1 side chain on alpha-helical segments suggest that V1 side chains adopt only a few discrete rotamers. In most cases, only one rotamer is observed at a given site, explaining the frequently observed narrow distance distribution for doubly V1-labeled proteins. We used the present data to derive guidelines that may allow distance interpretation of other V1-labeled proteins for higher-precision structural modeling.

Toward Precise Interpretation of DEER-Based Distance Distributions: Insights from Structural Characterization of V1 Spin-Labeled Side Chains.,Balo AR, Feyrer H, Ernst OP Biochemistry. 2016 Sep 20;55(37):5256-63. doi: 10.1021/acs.biochem.6b00608. Epub , 2016 Sep 2. PMID:27532325^[2]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.