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Page 416<br />

positions of the β bulge and Asp145 are observed [42] with the two regions separated <strong>by</strong> the known IL-<br />

1RI binding site.<br />

We have compiled the available site-directed mutants of IL-1β and sorted them according to the<br />

following four categories: (1) mutants that shows significantly higher agonistic activity, A1T, P2M,<br />

S5R, N89G, K92R, and K93R; (2) mutants that show significantly higher antagonistic activity, R4E,<br />

C8S, T9G, T9Q, T9E, L10T,C,S,A, C71X, R11G, K93M, M95R, E96Q, K103Q, and D145K;, (3)<br />

mutants that show significantly higher binding, A1T + P2M, S5R, T9L, T9W, P87S, P87H, K88V,G,L,<br />

N89R, E96Q, K103Q, G, C and M148A; and (4) mutants that show significantly lower binding,<br />

R4A,K,D, L6A, T9E, L10N,T,C,S,A, H30R, M44S, F46D, A, 156A, V58A, K92E, K93L,A,F,S,E,Q,L,<br />

K103S, and E105S,K. These four types of mutants are shown in Figure 11a–d.<br />

Taken together, this information supports our earlier proposal of the receptor-binding epitope. This was<br />

further characterized as functional sites A and B of interleukin-1. The first site, Area A is structurally<br />

conserved in all three molecules and contains residues Arg11, His30, and Asp145 in IL-1β Asn17,<br />

Ala36, and Asp147 in IL-1α; and Trp16, Tyr34, and Lys145 in IL-1Ra. Present in both active IL-1<br />

molecules, Asp145 has been recognized as an important residue in IL-1 binding. Area B has also been<br />

identified in both IL-1α and IL-1β it contains a large hydrophilic ridge around solvent-accessible<br />

hydrophobic residues. In-IL-1β, this region contains the 7-residue hydrophilic ridge (Arg4, Gln48,<br />

Glu51, Asn53, Lys93, Glu105, Asn108) around 5 hydrophobic solvent-accessible residues (Leu6,<br />

Val47, Ile56, Leu110, Val151). Figure 12 shows a surface presentation of the proposed receptor-binding<br />

epitope. In IL-1α, the 7-residue hydrophilic ridge has been identified with residues (Arg12, Ile14,<br />

Asp60, Asp61, Ile64, Lys96, and Trp109, which when mutated resulted in significant loss of binding to<br />

the receptor. Area B is structurally conserved in IL-1β and in IL-1α, but is lacking in IL-1Ra. For this<br />

reason Area A has been proposed as the binding region while Area B has been proposed as the<br />

triggering region.<br />

D. Peptide Fragments<br />

Peptide-<strong>based</strong> IL-1 antagonists have been derived from the primary sequence of IL-1α or IL-1β.<br />

Stepwise synthesis of a series of peptides from amino-terminal to carboxy-terminal regions did not<br />

provide any satisfactory results [68]. Polypeptide fragments of IL-1β, termed somnogeneic peptides,<br />

induced sleep in mammals [69], 61.5% NREMS at a dose of 20 ng. The numbering of these peptides in<br />

proIL-1 are 178–207, 199–225, 208–240 and that of mature IL-1β are 62–91, 83–109, and 92–124 (seq<br />

92–124=KKKMEKRFVFNKIENNKLEFESAQFPNWYIST). Monsanto company has identified a<br />

peptide fragment of IL-1β (41–70) exhibiting inhibitory effects for IL-1β and IL-1β, but not TNF-α, at 5<br />

nM (5 ng/mL). Peptide 56–70 is a<br />

http://legacy.netlibrary.com/nlreader/nlReader.dll?bookid=12640&filename=Page_416.html [4/5/2004 5:48:12 PM]

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