High Accuracy of Karplus Equations for Relating Three‐Bond J Couplings to Protein Backbone Torsion Angles. Issue 3 (15th December 2014)

• Record Type: Journal Article
• Authors: Li, Fang; Lee, Jung Ho; Grishaev, Alexander; Ying, Jinfa; Bax, Ad
• Is Part Of: Chemphyschem. Volume 16:Issue 3(2015)
• Page Start: 572
• Page End: 578
• Publication Date: 2014-12-15
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.05
• DOI: 10.1002/cphc.201402704
• Languages: English
• ISSNs: 1439-4235

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p> <sup>3</sup> <italic>J</italic> <sub>C′C′</sub> and <sup>3</sup><italic>J</italic><sub>HNHα</sub> couplings are related to the intervening backbone torsion angle <inline-formula><alternatives><tex-math notation="tex"><![CDATA[${\varphi }$]]></tex-math><inline-graphic xlink:href="ark:/27927/pgh3wbpqfds" mimetype="image" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /></alternatives></inline-formula> by standard Karplus equations. Although these couplings are known to be affected by parameters other than <inline-formula><alternatives><tex-math notation="tex"><![CDATA[${\varphi }$]]></tex-math><inline-graphic xlink:href="ark:/27927/pgh3wbpqfbp" mimetype="image" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /></alternatives></inline-formula>, including H‐bonding, valence angles and residue type, experimental results and quantum calculations indicate that the impact of these latter parameters is typically very small. The solution NMR structure of protein GB3, newly refined by using extensive sets of residual dipolar couplings, yields 50–60 % better Karplus equation agreement between <inline-formula><alternatives><tex-math notation="tex"><![CDATA[${\varphi }$]]></tex-math><inline-graphic xlink:href="ark:/27927/pgh3wbpqf94" mimetype="image" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /></alternatives></inline-formula> angles and experimental <sup>3</sup><italic>J</italic><sub>C′C′</sub> and <sup>3</sup><italic>J</italic><sub>HNHα</sub> values than does the high‐resolution X‐ray structure. In intrinsically disordered proteins, <sup>3</sup><italic>J</italic><sub>C′C′</sub> and <sup>3</sup><italic>J</italic><sub>HNHα</sub> couplings can be measured at even higher accuracy, and the impact of factors other than the intervening torsion angle on <sup>3</sup><italic>J</italic> will be smaller than in folded proteins, making these couplings exceptionally valuable reporters on the ensemble of <inline-formula><alternatives><tex-math notation="tex"><![CDATA[${\varphi }$]]></tex-math><inline-graphic xlink:href="ark:/27927/pgh3wbpqfkj" mimetype="image" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /></alternatives></inline-formula> angles sampled by each residue.</p> </abstract>