A 13C nuclear magnetic resonance study of histone H1 in 2-chloroethanol and aqueous solutions. Identification of peaks characteristic of secondary folding.
A 13C NMR study of calf thymus histone H1 in both aqueous solution and 2-chloroethanol solution was performed to clarify the folding behavior in these systems. To ascertain the general trend of displacements of 13C shifts upon folding in an enhanced manner, the latter solvent was employed since it is known to increase the amount of alpha-helix content in histone to about 50%. Generally, upfield displacements of C beta signals (up to 1.4 ppm) were clearly identified as helix-induced peaks, although displacements of C alpha signals, which might be much larger, were not easily distinguished because of overlap of several broadened signals with reduced peak intensities. In particular, we found that the upfield displacement of Ala C beta, by 1.1 ppm, is an excellent probe to monitor the presence of alpha-helix conformation in both 2-chloroethanol and aqueous solutions. This upfield displacement of the C beta signal in alpha-helix segment is consistent with our previous findings for a number of model polypeptides by ordinary and solid-state high resolution 13C NMR spectroscopy. Further, we observed that 13C peaks of several residues (Tyr, Ser, Leu, Ile, and Val) were suppressed as a result of specific folding of H1 in the presence of NaCl in aqueous solution. Thus, it appears that several tightly-folded segments whose 13C signals were considerably broadened are located in the central core portion.
D000596:Amino Acids; D000818:Animals; D002417:Cattle; D002728:Chlorohydrins; D005023:Ethylene Chlorohydrin; D006657:Histones; D009682:Magnetic Resonance Spectroscopy; D011487:Protein Conformation; D012996:Solutions; D013950:Thymus Gland; D014867:Water
D000596:Amino Acids; D002728:Chlorohydrins; D006657:Histones; D012996:Solutions; D014867:Water; D005023:Ethylene Chlorohydrin