Comparison of fast backbone dynamics at amide nitrogen and carbonyl sites in dematin headpiece C-terminal domain and its S74E mutant
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We perform a detailed comparison of fast backbone dynamics probed at amide nitrogen versus carbonyl carbon sites for dematin headpiece C-terminal domain (DHP) and its S74E mutant (DHPS74E). Carbonyl dynamics is probed via auto-correlated longitudinal rates and transverse C′/C′-Cα CSA/dipolar and C′/C′–N CSA/dipolar cross-correlated rates, while 15N data are taken from a previous study. Resulting values of effective order parameters and internal correlation times support the conclusion that C′ relaxation reports on a different subset of fast motions compared to those probed at N–H bond vectors in the same peptide planes. 13C′ order parameters are on the average 0.08 lower than 15N order parameters with the exception of the flexible loop region in DHP. The reduction of mobility in the loop region upon the S74E mutation can be seen from the 15N order parameters but not from the 13C order parameters. Internal correlation times at 13C′ sites are on the average an order of magnitude longer than those at 15N sites for the well-structured C-terminal subdomains, while the more flexible N-terminal subdomains have more comparable average internal correlation times.
KeywordsDematin headpiece NMR relaxation Backbone dynamics Carbonyl dynamics Fast motions Model-free
We are indebted to Prof. C. James McKnight for providing the protein samples and to Prof. Arthur G. Palmer for providing spectrometer time. We are grateful to Prof. Erik Zuiderweg for an access to the COMFORD program and to Dr. Philippe Pelupessy for the guidance on the cross-correlated relaxation pulse sequences. LV acknowledges University of Alaska funds 104110-11970&11470.
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