Molecular and channel-forming characteristics of gramicidin K's: a family of naturally occurring acylated gramicidins

WILLIAMS, L. PEARCE; Narcessian, E J; Andersen, Olaf S.; Waller, George R.; Taylor, Melissa J.; Lazenby, J P; Hinton, James F.; Koeppe, Roger E.

doi:10.1021/bi00147a015

Cited by 18 publications

(19 citation statements)

References 37 publications

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“…Also labeled in Figure 2 are the long-range NOESY cross peaks that are indicative of a right-handed /363 helix, NH,-CaH,+6 for even i and NH,-CaH,-6 for odd i (Arsen 'ev et al, 1985;Koeppe et al, 1994b). This NMR evidence for the retention of backbone structure is in agreement with previous data that include the similar circular diehroism spectra of gA and acyl-gA (Vogt et al, 1991) and the hybrid channel formation between acyl-gA and right-handed /363helical reference compounds (Williams et al, 1992).…”

Section: Resultssupporting

confidence: 91%

“…Functionally, the acylation of gA does not alter the singlechannel conductance for Na+ or Cs+, but it does increase the mean channel lifetime 5-fold (Koeppe et al, 1985;Vogt et al, 1992). Previous studies have demonstrated that acylation does not notably affect the structure of the gA backbone (Vogt et al, 1991(Vogt et al, , 1992Koeppe et al, 1992;Williams et al, 1992). Nothing is known about the possible influence of acylation on the orientation and dynamics of side chains.…”

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confidence: 98%

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Palmitoylation-Induced Conformational Changes of Specific Side Chains in the Gramicidin Transmembrane Channel

Koeppe¹,

Killian²,

Vogt³

et al. 1995

Biochemistry

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To gain insight into the structural consequences of acylation for membrane proteins, we have covalently attached palmitic acid to the ethanolamine end of gramicidin A (gA), which functions as a well-characterized cation-selective membrane channel. Next, we investigated by NMR methods the effect of acylation on the side chains of Trp9, Leu10, and Trp11, which are expected to be close to the acyl chain, and of Val7, which is expected to be far from the acyl chain. Two-dimensional NMR spectroscopy in a sodium dodecyl sulfate (SDS) environment suggests that one of the beta-hydrogens of Leu10 of gA is severely shielded by a nearby aromatic ring. This shielding disappears upon acylation. Deuterium NMR spectra for labeled samples in hydrated dimyristoylphosphatidylcholine (DMPC) bilayers show that, for the major gA conformation, the (deuterated) side chains of Trp9 and Leu10 are markedly influenced by acylation, whereas the side chains of Val7 and Trp11 are essentially unaffected. The NMR results in both environments suggest that the indole ring of Trp9 is situated near the side chain of Leu10 and moves away upon acylation. We propose that acylation provides a subtle mechanism to modulate protein and lipid interactions and to regulate the stability and function of proteins within membranes.

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Section: Resultssupporting

confidence: 91%

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confidence: 98%

Palmitoylation-Induced Conformational Changes of Specific Side Chains in the Gramicidin Transmembrane Channel

Koeppe¹,

Killian²,

Vogt³

et al. 1995

Biochemistry

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“…The convergent results also suggest that the gA channel structures in SDS and DMPC environments are highly similar. The solid-state approach, due to its high sensitivity, will also prove valuable as a difference method for examining the effects of sequence changes (e.g., Durkin et al, 1990), fatty acylation (Williams et al, 1992;Vogt et al, 1992;Koeppe et al, 1993), or other covalent modifications to the gramicidin channel. Side chain-side chain and side chain-lipid interactions are expected to be revealed through changes in the 2H NMR spectra that reflect different side chain orientations and/or dynamics.…”

Section: Comparison Of Nmr Methodsmentioning

confidence: 99%

Orientations of the tryptophan 9 and 11 side chains of the gramicidin channel based on deuterium nuclear magnetic resonance spectroscopy

Koeppe¹,

Killian²,

Greathouse³

1994

Biophysical Journal

117

212

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Deuterium nuclear magnetic resonance spectroscopy was used to investigate the orientations of the indole rings of Trp9 and Trp11 in specific indole-d5-labeled samples of gramicidin A incorporated into dimyristoyl phosphatidylcholine bilayers in the beta 6.3 channel conformation. The magnitudes and signs of the deuterium quadrupolar splittings were fit to the rings and assigned to specific ring bonds, using a full rotation search of the chi 1 and chi 2 angles of each Trp and a least-squares method. Unique assignments were obtained. The data and assignments are in close agreement with four sets of (chi 1, chi 2) angles for each Trp in which the indole N-H is oriented toward the membrane's exterior surface. (Four additional sets of (chi 1, chi 2) angles with the N-H's pointing toward the membrane interior are inconsistent with previous observations.) One of the sets of (chi 1, chi 2) angles for each Trp is consistent with the corresponding Trp orientation found by Arsen'ev et al. (1986. Biol. Membr. 3:1077-1104) for gramicidin in sodium dodecyl sulfate micelles. Together, the 1H and 2H nuclear magnetic resonance methods suggest that the Trp9 and Trp11 side chain orientations could be very similar in dimyristoyl phosphatidylcholine membranes and in sodium dodecyl sulfate micelles. The data for Trp11 could be fit using a static quadrupolar coupling constant of 180 kHz under the assumption that the ring is essentially immobile. By contrast, Trp9 could be fit only under the assumption that the quadrupolar splittings for ring 9 are reduced by approximately 14% due to motional averaging. Such a difference in motional averaging between rings 11 and 9 is also consistent with the 15N data of Hu et al. (1993. Biochemistry. 32:7035-7047).

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“…It is thought that the variation in dipole moments affect long range ion-dipole interactions critical for ion conduction. In addition, variation of the amino acid residue at position 11 (e.g., Trp, Phe, or Tyr) also induces changes in the average lifetime of channel species (Mazet et al, 1984;Becker et al, 1991;Williams et al, 1992;Andersen et al, 1998). The average single-channel lifetime is a measure of the gramicidin dimer dissociation rate constant (Becker et al, 1991), and provides a measure of channel stability in a bilayer mimetic.…”

Section: Introductionmentioning

confidence: 99%

Effects of Phenylalanine Substitutions in Gramicidin A on the Kinetics of Channel Formation in Vesicles and Channel Structure in SDS Micelles

Jordan

Easton

Hinton

2005

Biophysical Journal

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The common occurrence of Trp residues at the aqueous-lipid interface region of transmembrane channels is thought to be indicative of its importance for insertion and stabilization of the channel in membranes. To further investigate the effects of Trp-->Phe substitution on the structure and function of the gramicidin channel, four analogs of gramicidin A have been synthesized in which the tryptophan residues at positions 9, 11, 13, and 15 are sequentially replaced with phenylalanine. The three-dimensional structure of each viable analog has been determined using a combination of two-dimensional NMR techniques and distance geometry-simulated annealing structure calculations. These phenylalanine analogs adopt a homodimer motif, consisting of two beta6.3 helices joined by six hydrogen bonds at their NH2-termini. The replacement of the tryptophan residues does not have a significant effect on the backbone structure of the channels when compared to native gramicidin A, and only small effects are seen on side-chain conformations. Single-channel conductance measurements have shown that the conductance and lifetime of the channels are significantly affected by the replacement of the tryptophan residues (Wallace, 2000; Becker et al., 1991). The variation in conductance appears to be caused by the sequential removal of a tryptophan dipole, thereby removing the ion-dipole interaction at the channel entrance and at the ion binding site. Channel lifetime variations appear to be related to changing side chain-lipid interactions. This is supported by data relating to transport and incorporation kinetics.

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Molecular and channel-forming characteristics of gramicidin K's: a family of naturally occurring acylated gramicidins

Cited by 18 publications

References 37 publications

Palmitoylation-Induced Conformational Changes of Specific Side Chains in the Gramicidin Transmembrane Channel

Palmitoylation-Induced Conformational Changes of Specific Side Chains in the Gramicidin Transmembrane Channel

Orientations of the tryptophan 9 and 11 side chains of the gramicidin channel based on deuterium nuclear magnetic resonance spectroscopy

Effects of Phenylalanine Substitutions in Gramicidin A on the Kinetics of Channel Formation in Vesicles and Channel Structure in SDS Micelles

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