Structure - Function relationships in side chain lactam cross-linked peptide models of a conserved N-terminal domain of apolipoprotein E

Tammie L.S. Benzinger, Demetrios T. Braddock, Samuel R. Dominguez, Timothy S. Burkoth, Hélène Miller-Auer, Ram M. Subramanian, Gunther M. Fless, David N.M. Jones, David G. Lynn, Stephen C. Meredith

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8 Scopus citations

Abstract

Bioactive peptides have multiple conformations in solution but adopt well-defined conformations at lipid surfaces and in interactions with receptors. We have used side chain lactam cross-links to stabilize secondary structures in the following peptide models of a conserved N-terminal domain of apolipoprotein E (cross-link periodicity in parentheses): I, H2N- GQTLSEQVQEELLSSQVTQELRAG-COOH (none); III, H2N-GDTLKEQVQEELLSEQVKDELKAG- COOH (i to i + 3); IV, H2N-GQDLSEKVQEELLESQVK-DELLKAG-COOH (i to i + 4); IVa, H2N-GQDLSEKVQEELLSEQVKDELLKAG-COOH (i to i + 4) (lactams above the sequence, potential salt bridges below the sequence). We previously demonstrated [Luo et al. (1994) Biochemistry 33, 12367-12377; Braddock et al. (1996) Biochemistry 35, 1397513984] that peptide III, containing lactam cross-links between the i and i + 3 side chains, enhances specific binding of LDL via a receptor other than the LDL-receptor. Peptide III in solution consists of two short α helices connected by a non α helical segment. Here we examine the hypothesis that the domain modeled by peptide III is one antipode of a conformational switch. To model another antipode of the switch, we introduced two strategic modifications into peptide III to examine structure-function relationships in this domain: (1) the spacing of the lactam cross-links was changed (i to i + 4 in peptides IV and IVa) and (2) peptides IV and IVa contain the two alternative sequences at a site of a possible end-capping interaction in peptide III. The structure of peptide IV, determined by 2D-NMR, is α helical across its entire length. Despite the remarkable degree of structural order, peptide IV is biologically inactive. In contrast, peptides III and possibly IVa contain a central interruption of the α helix, which appears necessary for biological activity. These and other studies support the hypothesis that this domain is a conformational switch which, to the extent that it models apolipoprotein E itself, may modulate interactions between apo E and its various receptors.

Original languageEnglish
Pages (from-to)13222-13229
Number of pages8
JournalBiochemistry
Volume37
Issue number38
DOIs
StatePublished - Sep 22 1998
Externally publishedYes

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    Benzinger, T. L. S., Braddock, D. T., Dominguez, S. R., Burkoth, T. S., Miller-Auer, H., Subramanian, R. M., Fless, G. M., Jones, D. N. M., Lynn, D. G., & Meredith, S. C. (1998). Structure - Function relationships in side chain lactam cross-linked peptide models of a conserved N-terminal domain of apolipoprotein E. Biochemistry, 37(38), 13222-13229. https://doi.org/10.1021/bi980482f