Deletion mutants of human interleukin 1 beta with significantly reduced agonist properties: search for the agonist/antagonist switch in ligands to the interleukin 1 receptors.
The existence of an endogenous high affinity interleukin 1 receptor antagonist (IL-1ra) suggests that this molecule lacks some structural motif(s) which are present in the closely homologous agonist interleukin 1 beta (IL-1 beta) and which serve as the 'agonist switch' causing signal transduction by the agonist-receptor complex. The primary sequence alignment of IL-1 beta and IL-1ra sequences from different species reveals a six amino acid long motif that is quasi conserved among IL-1 beta sequences, but is missing from the IL-1ra sequences. The three-dimensional structure of human IL-1 beta was used as a template for building structural models of deletion mutants (delta SND 52-54 and delta EESNDK 50-55) using molecular graphics. These models indicated that the middle three residues SND 52-54 from the EESNDK 50-55 loop may be deleted without causing major changes in the tertiary structure of the mutant as compared to that of IL-1 beta. Residues SND 52-54 from the above loop were deleted. When compared with IL-1 beta the IL-1 beta-delta SND analog (delta SND 52-54) binds with the same affinity to type 2 IL-1 receptor but with a more than 10-fold lower affinity to type 1 IL-1 receptor. Despite of this small decrease in affinity at the type 1 receptor the delta SND 52-54 has a 1000-fold lower biological activity than IL-1 beta when tested in a thymocyte activating factor assay.(ABSTRACT TRUNCATED AT 250 WORDS)
Simoncsits
A
A
Department of Neurochemistry and Neurotoxicology, Stockholm University, Sweden.
Bristulf
J
J
Tjörnhammar
M L
ML
Cserzö
M
M
Pongor
S
S
Rybakina
E
E
Gatti
S
S
Bartfai
T
T
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001667:Binding, Competitive; D002417:Cattle; D017931:DNA Primers; D006801:Humans; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1 / Q000737:chemistry* / Q000378:metabolism*; D008024:Ligands; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016296:Mutagenesis; D017433:Protein Structure, Secondary; D011817:Rabbits; D051381:Rats; D017472:Receptors, Interleukin-1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D012756:Sheep; D012795:Sialoglycoproteins / Q000737:chemistry* / Q000378:metabolism*
D017931:DNA Primers; C507763:IL1RN protein, human; C507764:Il1rn protein, mouse; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1; D008024:Ligands; D017472:Receptors, Interleukin-1; D011994:Recombinant Proteins; D012795:Sialoglycoproteins