TY - JOUR
T1 - Structure - Function relationships in side chain lactam cross-linked peptide models of a conserved N-terminal domain of apolipoprotein E
AU - Benzinger, Tammie L.S.
AU - Braddock, Demetrios T.
AU - Dominguez, Samuel R.
AU - Burkoth, Timothy S.
AU - Miller-Auer, Hélène
AU - Subramanian, Ram M.
AU - Fless, Gunther M.
AU - Jones, David N.M.
AU - Lynn, David G.
AU - Meredith, Stephen C.
PY - 1998/9/22
Y1 - 1998/9/22
N2 - 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.
AB - 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.
UR - https://www.scopus.com/pages/publications/0032558461
U2 - 10.1021/bi980482f
DO - 10.1021/bi980482f
M3 - Article
C2 - 9748329
AN - SCOPUS:0032558461
SN - 0006-2960
VL - 37
SP - 13222
EP - 13229
JO - Biochemistry
JF - Biochemistry
IS - 38
ER -