The design and synthesis of nonpeptide compounds as mimics of a conformation of methionine-enkephaline

Abstract

A model for the active conformation of methionine-enkephalin containing a P-turn was derived from computer modeling. Using a trans-perhydronaphthalene as a structural template and a mimic of the p-turn, target compounds were designed and synthesized. Thus, a key intermediate, trans-3-oxo-5~-formamidomethyl-8a-phenylmethylperhydronaphthalene, was prepared by two different routes from cyclohexanone.The addition of a methionine-like side-chain to this key intermediate was best achieved by a reaction with the anion of methyl 2-trimethylsilyl-4-methylthiobutanoate. This led to the preparation of an exo-tetrasubstituted double bond in high yield. Subsequent addition of tyrosine through coupling with the 5P-aminomethyl group provided the desired perhydronaphthalene mimics of met-enkaphalin.

The solution structure of the viral binding domain of Tva, the cellular receptor for subgroup A avian leukosis and sarcoma virus1

“…Purified sTva47 required oxidative folding to form the correct disulfide bonds. As was found for oxidation of LBr from the LDLR family of receptors [12,17,18,20], calcium was required to selectively form a single disulfide bonding pattern, which we assumed matched that of the native Tva and the LDLR LBr as previously suggested [9] (Wang et al have reported similar findings [23]). After suitable conditions were defined, oxidation was carried out using purified MBP–sTva47 in order to use correctly oxidized sTva47 attached to MBP for surface plasmon resonance binding experiments (see below).…”

“…NOE cross‐peak connectivities and preliminary structural calculations suggested a unique disulfide bonding pattern in agreement with the topology suggested by mutagenic studies [9] and comparison to other LDLR LBrs. Hence, the three disulfide bonds were defined for further structural calculations with DYANA and AMBER.…”

“…Most of these residues are located in the C‐terminal portion of the protein suggesting that this is where the bulk of the viral binding site is located. Among them are highly conserved residues that are critical to ensure proper folding of the LBr module of Tva: D46 and E47, whose acidic side chains coordinate calcium [23,37], and C35 and C50, that form a disulfide bridge [9]. Mutations of these residues most likely exert their effect by disrupting the Tva structure at the viral binding site.…”

“…This ∼40 aa LDLR ligand binding repeat (LBr) is sufficient to reconstitute ALSV‐A cell entry [8]. Mutational analysis of the cysteines in the Tva LDLR LBr suggested a first–third, second–fifth, and fourth–sixth disulfide bonding pattern [9], which matches that later determined for the LBr of LDLR [10–12]. Intriguingly, further mutational analysis has suggested that tryptophan 48 (W48) serves a critical role in post‐binding events required for the viral fusion protein to assume a liposome binding conformation [13] and for viral cell entry [14].…”

Conversion of a human low-density lipoprotein receptor ligandbinding repeat to a virus receptor: Identification of residues important for ligand specificity

“…2B, lanes 2-14). Although there is some variation in the receptor levels of the mutants, all are expressed well above the minimum level required for full viral receptor function by wt Tva (21). The numerous bands observed for wt Tva, TL4, and the TL4 mutants are most likely a result of modification by N-and O-glycosylation, which has been observed previously with wt Tva (H. Wang, D. Chu, K.G., H. E. Varmus, and P.B., unpublished data).…”