1995
DOI: 10.1021/bi00036a038 View full text |Buy / Rent full text
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Abstract: Proteins that are destined for export out of the cytoplasm of Escherichia coli cells are synthesized as precursor proteins with N-terminal extensions or signal sequences, which are essential for translocation of the protein across the inner membrane. Signal sequences contain very little primary sequence homology, and therefore recognition of these sequences is thought to involve specific folding. To assess the conformational flexibility of signal sequences, we have studied the signal peptide of PhoE (MKKSTLALV… Show more

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“…Comparison of the conformation of the peptide in two different micelle systems by comparing the secondary structure-sensitive interresidue NOE cross-peaks was hampered by cross-peak overlap problems and by quantification difficulties due to dynamical effects. The intensities of the medium range NOEs for p25 are relatively low compared with those for the bacterial signal peptides of OmpA [34] or PhoE [35] associated with similar micelles. This can be explained by the fact that p25 is less hydrophobic than the bacterial signal peptides, resulting in a dynamical equilibrium between water-soluble (random coil) and micelle-bound (~-helicab forms of p25.…”
Section: Resultsmentioning
“…The aim of the work described here is threefold: (i) to confirm that M. tuberculosis Cpn10 is secreted from M. tuberculosis; (ii) to study the structural preferences of M. tuberculosis Cpn10 under conditions similar to those experienced by the protein when it approaches the lipid-water interface or crosses the hydrophobic lipid bilayer of the cytosolic membrane (7,12,19), and (iii) to understand whether any relationship at all exists between these structures and M. tuberculosis Cpn10 secretion. To achieve these aims, macrophages have been infected with virulent M. tuberculosis and the intracellular localization of the M. tuberculosis Cpn10 has been determined by immunogold labeling.…”
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“…The latter may not be physiologically relevant. Nevertheless, H͞D exchange rates have been measured for individual assigned amide protons of various membrane-associated peptides and proteins in detergent solutions (6)(7)(8)(9). Another NMR approach makes use of trapping techniques and subsequent transfer of the peptide from an aqueous membrane environment to isotropic media (10).…”
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“…Dipolar interactions are not averaged out and the NMR lines are significantly broadened, which makes high-resolution NMR studies of membrane proteins in lipid bilayers impossible to carry out. To circumvent this problem, membrane-associated peptides can often be dissolved in organic solvents, which are assumed to approximate the hydrophobic environment of a lipid bilayer (Bruch et al, 1989;Yamamoto et al, 1990;Rizo et al, 1993;Wolff et al, 1994;Chupin et al, 1995;Zhang et al, 1995). While such lowviscous, isotropic solutions often allow spectroscopic studies to be carried out, it is desirable to perform structural studies with peptide segments from membrane proteins in environments that more closely resemble the native membrane.…”
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“…A hypothesis was proposed that the positively charged N terminus enables the signal peptide to bind to anionic phospholipid headgroups, inserting its hydrophobic core into bilayer with the aid of acidic lipid (14 -16). The insertion of signal peptide into membrane is accompanied by a formation of helixbreak-helix motif (17), presumably forming a non-bilayer lipid structure as with model membranes (18). The change in membrane structure by signal peptide appears to rely on its competence to export in vivo, because the non-functional signal peptide failed to destabilize the bilayer structure.…”
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