Structure and function of chicken interleukin-1 beta mutants: uncoupling of receptor binding and in vivo biological activity.
Receptor-binding and subsequent signal-activation of interleukin-1 beta (IL-1β) are essential to immune and proinflammatory responses. We mutated 12 residues to identify sites important for biological activity and/or receptor binding. Four of these mutants with mutations in loop 9 (T117A, E118K, E118A, E118R) displayed significantly reduced biological activity. Neither T117A nor E118K mutants substantially affected receptor binding, whereas both mutants lack the IL-1β signaling in vitro but can antagonize wild-type (WT) IL-1β. Crystal structures of T117A, E118A, and E118K revealed that the secondary structure or surface charge of loop 9 is dramatically altered compared with that of wild-type chicken IL-1β. Molecular dynamics simulations of IL-1β bound to its receptor (IL-1RI) and receptor accessory protein (IL-1RAcP) revealed that loop 9 lies in a pocket that is formed at the IL-1RI/IL-1RAcP interface. This pocket is also observed in the human ternary structure. The conformations of above mutants in loop 9 may disrupt structural packing and therefore the stability in a chicken IL-1β/IL-1RI/IL-1RAcP signaling complex. We identify the hot spots in IL-1β that are essential to immune responses and elucidate a mechanism by which IL-1β activity can be inhibited. These findings should aid in the development of new therapeutics that neutralize IL-1 activity.
Institute of Bioinformatics and Structural Biology, and College of Life Sciences, National Tsing Hua University, No. 101, Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan.
Wen-Ting
WT
Chen
Institute of Bioinformatics and Structural Biology, and College of Life Sciences, National Tsing Hua University, No. 101, Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan.
Wen-Yang
WY
Huang
Institute of Bioinformatics and Structural Biology, and College of Life Sciences, National Tsing Hua University, No. 101, Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan.
Ting
T
Chen
Institute of Bioinformatics and Structural Biology, and College of Life Sciences, National Tsing Hua University, No. 101, Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan.|Bioinformatics Program, Taiwan International Graduate Program, Academia Sinica, Taipei, 115, Taiwan.
Emmanuel Oluwatobi
EO
Salawu
School of Life Science, Tsing Hua University, Beijing, China.
Dongli
D
Wang
Institute of Bioinformatics and Structural Biology, and College of Life Sciences, National Tsing Hua University, No. 101, Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan.
Yi-Zong
YZ
Lee
Institute of Bioinformatics and Structural Biology, and College of Life Sciences, National Tsing Hua University, No. 101, Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan.
Yuan-Yu
YY
Chang
Institute of Bioinformatics and Structural Biology, and College of Life Sciences, National Tsing Hua University, No. 101, Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan.|Bioinformatics Program, Taiwan International Graduate Program, Academia Sinica, Taipei, 115, Taiwan.
Lee-Wei
LW
Yang
Institute of Bioinformatics and Structural Biology, and College of Life Sciences, National Tsing Hua University, No. 101, Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan.
Shih-Che
SC
Sue
School of Life Science, Tsing Hua University, Beijing, China.
Xinquan
X
Wang
Institute of Bioinformatics and Structural Biology, and College of Life Sciences, National Tsing Hua University, No. 101, Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan.
Hsien-Sheng
HS
Yin
D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D002645:Chickens / Q000235:genetics / Q000378:metabolism*; D018360:Crystallography, X-Ray; D005786:Gene Expression Regulation; D053577:Interleukin-1 Receptor Accessory Protein; D053583:Interleukin-1beta / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D009154:Mutation; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017472:Receptors, Interleukin-1 / Q000378:metabolism*
D053577:Interleukin-1 Receptor Accessory Protein; D053583:Interleukin-1beta; D017472:Receptors, Interleukin-1