Study of hydrogen bonding networks in proteins by high resolution NMR spectroscopy

摘要

From measured ~1J_(NC') coupling constants in three poteins (human ubiquitin, carp parvalbumin and rat intestinal fatty acid binding protein) characteristic sequences of the coupling constant are observed which correlate with the protein secondary and tertiary structure. In the α-helix, the coupling consant varies from 15.3 Hz to 15.8 Hz. Four carp parvalbumin helices show correlation of the ~1J_(NC') coupling constant with the exposure of the helices to the hydrophilic or hydrophobic environment. In β-sheets, variations of the ~1J_(NC') coupling constant are larger (15.5 ± 1.5 Hz). The central region of the parallel and antiparallel β-sheets exhibits correlation of the ~1J_(NC') coupling constants within the lines of interstrand C=O·ぁぁ-N hydrogen bonding. This indicates a cooperative character of H-bonding and demonstrates the existence of H-bonding network. The coupling constant most noticeably changes within reverse turns. In all three proteins the coupling constant has the lowest values at position 2 (14.3 ± 0.6 Hz), and the highest at position 4 (17.0 ± 0.5 Hz). This change of the coupling constant within the three residues of the reverse turn is caused by specific H-bonding of amide groups in the reverse turn, HOH~(solv)····O=C at position 4 and N-H····OH_2~(solv) at position 2. Observed correlations of the ~1J_(NC') coupling constant within and between the elements of secondary structure in proteins can be useful in protein structure determination and study of protein folding and stability.