Secondary structure and topology of interleukin-1 receptor antagonist protein determined by heteronuclear three-dimensional NMR spectroscopy.
Interleukin-1 (IL-1) proteins, such as IL-1 beta, play a key role in immune and inflammatory responses. Interaction of these cytokines with the IL-1 receptor induces a variety of biological changes in neurologic, metabolic, hematologic, and endocrinologic systems. Interleukin-1 receptor antagonist protein (IRAP) is a naturally occurring inhibitor of the interleukin-1 receptor. The 153-residue protein binds to the receptor with an affinity similar to that of IL-1 beta but does not elicit any physiological responses. As a first step toward understanding IRAP's mode of action, we have used multidimensional, heteronuclear NMR spectroscopy to determine the antagonist's solution secondary structure and global fold. Using a combination of 3D 1H-15N NOESY-HMQC and TOCSY-HMQC and 3D 1H-15N-13C HNCA and HN(CO)CA experiments on uniformly 15N- or doubly 13C/15N-enriched IRAP, we have made resonance assignments for more than 90% of the main-chain atoms. Analysis of short- and long-range NOE's indicates that IRAP is predominantly beta-sheet, with the same overall topology as IL-1 beta but with different regions of the primary sequence comprising the beta-strands. Two short helical segments also were identified. The 14% sequence identity between IL-1 beta and IRAP increases to 25% when differences in the locations of secondary structure elements in the primary sequences are taken into account. Still, numerous differences in side chains, which ultimately play a major role in receptor interaction, exist.(ABSTRACT TRUNCATED AT 250 WORDS)
Stockman
B J
BJ
Upjohn Laboratories, Upjohn Company, Kalamazoo, Michigan 49007.
Scahill
T A
TA
Roy
M
M
Ulrich
E L
EL
Strakalaitis
N A
NA
Brunner
D P
DP
Yem
A W
AW
Deibel
M R
MR
D000595:Amino Acid Sequence; D006801:Humans; D006860:Hydrogen Bonding; D066298:In Vitro Techniques; D053590:Interleukin 1 Receptor Antagonist Protein; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011506:Proteins / Q000648:ultrastructure*; D011971:Receptors, Immunologic / Q000037:antagonists & inhibitors; D017472:Receptors, Interleukin-1; D011994:Recombinant Proteins; D012795:Sialoglycoproteins
C507763:IL1RN protein, human; D053590:Interleukin 1 Receptor Antagonist Protein; D011506:Proteins; D011971:Receptors, Immunologic; D017472:Receptors, Interleukin-1; D011994:Recombinant Proteins; D012795:Sialoglycoproteins