Generation of biologically active interleukin-1 beta by proteolytic cleavage of the inactive precursor.
Interleukin-1 beta (IL-1 beta) is derived from an inactive precursor by proteolytic cleavage. To study IL-1 beta processing, we expressed the precursor in Escherichia coli, partially purified it, and used it as a substrate for various potentially relevant protease preparations. The precursor alone was virtually inactive, but incubation with membranes from human monocytes or myeloid cell lines yielded a 500-fold increase in IL-1 bioactivity. Western blot analysis of the incubated material showed that the 31,000-Da precursor is broken down to three major products, ranging from 17,400 to about 19,000 Da. The most active of these products is the smallest one, and it co-migrates during electrophoresis with mature IL-1 beta. Four purified known proteases were also tested for their effect on precursor IL-1 beta, and none of these products co-migrated with the mature protein. Chymotrypsin and Staphylococcus aureus protease yielded slightly larger products, which were highly active. Elastase and trypsin yielded substantially larger products, and these had little IL-1 activity. The products of three of the known proteases were identified by NH2-terminal sequencing. These results show conclusively that proteolysis of precursor IL-1 beta generates biological activity and that the cleavage must occur close to the mature NH2 terminus.
Black
R A
RA
Immunex Corporation, Seattle, Washington 98101.
Kronheim
S R
SR
Cantrell
M
M
Deeley
M C
MC
March
C J
CJ
Prickett
K S
KS
Wignall
J
J
Conlon
P J
PJ
Cosman
D
D
Hopp
T P
TP
D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics; D007375:Interleukin-1 / Q000235:genetics* / Q000302:isolation & purification; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010447:Peptide Hydrolases; D010957:Plasmids; D011498:Protein Precursors / Q000235:genetics* / Q000302:isolation & purification; D011499:Protein Processing, Post-Translational; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism
D007375:Interleukin-1; D011498:Protein Precursors; D011994:Recombinant Proteins; C043830:interleukin 1 precursor; D010447:Peptide Hydrolases