Helix-Capping Histidines: Diversity of N-H···N Hydrogen Bond Strength Revealed by (2h)JNN Scalar Couplings.

ABSTRACT: In addition to its well-known roles as an electrophile and general acid, the side chain of histidine often serves as a hydrogen bond (H-bond) acceptor. These H-bonds provide a convenient pH-dependent switch for local structure and functional motifs. In hundreds of instances, a histidine caps the N-terminus of α- and 310-helices by forming a backbone NH···Nδ1 H-bond. To characterize the resilience and dynamics of the histidine cap, we measured the trans H-bond scalar coupling constant, (2h)JNN, in several forms of Group 1 truncated hemoglobins and cytochrome b5. The set of 19 measured (2h)JNN values were between 4.0 and 5.4 Hz, generally smaller than in nucleic acids (~6-10 Hz) and indicative of longer, weaker bonds in the studied proteins. A positive linear correlation between (2h)JNN and

SUBMITTER: Preimesberger MR 

PROVIDER: S-EPMC4660981 | biostudies-literature | 2015 Nov

REPOSITORIES: biostudies-literature