Determination of the secondary structure and folding topology of human interleukin-4 using three-dimensional heteronuclear magnetic resonance spectroscopy.
The secondary structure of human recombinant interleukin-4 (IL-4) has been investigated by three-dimensional (3D) 15N- and 13C-edited nuclear Overhauser (NOE) spectroscopy on the basis of the 1H, 15N, and 13C assignments presented in the preceding paper [Powers, R., Garrett, D. S., March, C. J., Frieden, E. A., Gronenborn, A. M., & Clore, G. M. (1992) Biochemistry (preceding paper in this issue)]. Based on the NOE data involving the NH, C alpha H, and C beta H protons, as well as 3JHN alpha coupling constant, amide exchange, and 13C alpha and 13C beta secondary chemical shift data, it is shown that IL-4 consists of four long helices (residues 9-21, 45-64, 74-96, and 113-129), two small helical turns (residues 27-29 and 67-70), and a mini antiparallel beta-sheet (residues 32-34 and 110-112). In addition, the topological arrangement of the helices and the global fold could be readily deduced from a number of long-range interhelical NOEs identified in the 3D 13C-edited NOE spectrum in combination with the spatial restrictions imposed by three disulfide bridges. These data indicate that the helices of interleukin-4 are arranged in a left-handed four-helix bundle with two overhand connections.
Garrett
D S
DS
Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892.
Powers
R
R
March
C J
CJ
Frieden
E A
EA
Clore
G M
GM
Gronenborn
A M
AM
D000595:Amino Acid Sequence; D004220:Disulfides; D006801:Humans; D006860:Hydrogen Bonding; D015847:Interleukin-4 / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011994:Recombinant Proteins
D004220:Disulfides; D011994:Recombinant Proteins; D015847:Interleukin-4