1
|
PRASAD KU, TRAPANE TL, BUSATH D, SZABO G, URRY DW. Synthesis and characterization of 1-13C-DLeu12,14 gramicidin A. ACTA ACUST UNITED AC 2009. [DOI: 10.1111/j.1399-3011.1982.tb02605.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
2
|
Sham SS, Shobana S, Townsley LE, Jordan JB, Fernandez JQ, Andersen OS, Greathouse DV, Hinton JF. The structure, cation binding, transport, and conductance of Gly15-gramicidin A incorporated into SDS micelles and PC/PG vesicles. Biochemistry 2003; 42:1401-9. [PMID: 12578352 DOI: 10.1021/bi0204286] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
To further investigate the effect of single amino acid substitution on the structure and function of the gramicidin channel, an analogue of gramicidin A (GA) has been synthesized in which Trp(15) is replaced by Gly in the critical aqueous interface and cation binding region. The structure of Gly(15)-GA incorporated into SDS micelles has been determined using a combination of 2D-NMR spectroscopy and molecular modeling. Like the parent GA, Gly(15)-GA forms a dimeric channel composed of two single-stranded, right-handed beta(6.3)-helices joined by hydrogen bonds between their N-termini. The replacement of Trp(15) by Gly does not have a significant effect on backbone structure or side chain conformations with the exception of Trp(11) in which the indole ring is rotated away from the channel axis. Measurement of the equilibrium binding constants and Delta G for the binding of monovalent cations to GA and Gly(15)-GA channels incorporated into PC vesicles using (205)Tl NMR spectroscopy shows that monovalent cations bind much more weakly to the Gly(15)-GA channel entrance than to GA channels. Utilizing the magnetization inversion transfer NMR technique, the transport of Na(+) ions through GA and Gly(15)-GA channels incorporated into PC/PG vesicles has been investigated. The Gly(15) substitution produces an increase in the activation enthalpy of transport and thus a significant decrease in the transport rate of the Na(+) ion is observed. The single-channel appearances show that the conducting channels have a single, well-defined structure. Consistent with the NMR results, the single-channel conductances are reduced by 30% and the lifetimes by 70%. It is concluded that the decrease in cation binding, transport, and conductance in Gly(15)-GA results from the removal of the Trp(15) dipole and, to a lesser extent, the change in orientation of Trp(11).
Collapse
Affiliation(s)
- S S Sham
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701, and Department of Physiology and Biophysics, Cornell University, Weill Medical College, New York, New York 10021
| | | | | | | | | | | | | | | |
Collapse
|
3
|
Townsley LE, Tucker WA, Sham S, Hinton JF. Structures of gramicidins A, B, and C incorporated into sodium dodecyl sulfate micelles. Biochemistry 2001; 40:11676-86. [PMID: 11570868 DOI: 10.1021/bi010942w] [Citation(s) in RCA: 169] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Gramicidins A, B, and C are the three most abundant, naturally occurring analogues of this family of channel-forming antibiotic. GB and GC differ from the parent pentadecapeptide, GA, by single residue mutations, W11F and W11Y, respectively. Although these mutations occur in the cation binding region of the channel, they do not affect monovalent cation specificity, but are known to alter cation-binding affinities, thermodynamic parameters of cation binding, conductance and the activation energy for ion transport. The structures of all three analogues incorporated into deuterated sodium dodecyl sulfate micelles have been obtained using solution state 2D-NMR spectroscopy and molecular modeling. For the first time, a rigorous comparison of the 3D structures of these analogues reveals that the amino acid substitutions do not have a significant effect on backbone conformation, thus eliminating channel differences as the cause of variations in transport properties. Variable positions of methyl groups in valine and leucine residues have been linked to molecular motions and are not likely to affect ion flow through the channel. Thus, it is concluded that changes in the magnitude and orientation of the dipole moment at residue 11 are responsible for altering monovalent cation transport.
Collapse
Affiliation(s)
- L E Townsley
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701, USA
| | | | | | | |
Collapse
|
4
|
Greathouse DV, Hinton JF, Kim KS, Koeppe RE. Gramicidin A/short-chain phospholipid dispersions: chain length dependence of gramicidin conformation and lipid organization. Biochemistry 1994; 33:4291-9. [PMID: 7512381 DOI: 10.1021/bi00180a025] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Gramicidin-lipid interactions were investigated using diacylphosphatidylcholines that contained two identical acyl chains of varying length, between 6 and 14 carbons. The gramicidin A (gA) conformation was monitored by circular dichroism (CD) spectroscopy and high-performance size-exclusion chromatography, and the lipid organization was investigated using 31P and 1H NMR spectroscopy and negative-stain electron microscopy. Diacylphosphatidylcholine (PC) lipids with chain lengths between 4 and 8 carbons have been previously shown to have a micellar organization in aqueous solution [Lin, T.-L., et al. (1986) J. Am. Chem. Soc. 108, 3499-3507]. CD spectra of aqueous gA/lipid dispersions, at a ratio of 1:28, demonstrated that the channel conformation of gA can be readily obtained when the acyl chain length is > or = 10, but not when the chain length is < or = 7. Size-exclusion chromatography revealed that the fraction of gA that could easily be dissociated into monomers in the dispersions increased with increasing acyl chain length, in agreement with the CD results. For a chain length of 8, the results were intermediate. The formation of the channel structure was found to depend on the "solvent-history", the temperature, the gA and lipid concentrations, the gA:lipid ratio, and consequently on the method of sample preparation. 1H and 31P NMR results suggest that codispersed gA increases the size of dioctanoyl-PC aggregates, but not of dihexanoyl-PC micelles. Negative-stain electron microscopy directly supports these findings. Dihexanoyl-PC (28 mM) was able to solubilize 1 mM gA in H2O, but the gA was not in the "channel" conformation.(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
Affiliation(s)
- D V Greathouse
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville 72701
| | | | | | | |
Collapse
|
5
|
Affiliation(s)
- J A Killian
- Department of Biochemistry of Membranes, University of Utrecht, Netherlands
| |
Collapse
|
6
|
Cox KJ, Ho C, Lombardi JV, Stubbs CD. Gramicidin conformational studies with mixed-chain unsaturated phospholipid bilayer systems. Biochemistry 1992; 31:1112-7. [PMID: 1370909 DOI: 10.1021/bi00119a020] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The transition of gramicidin from a nonchannel to a channel form was investigated using mixed-chain phosphatidylcholine lipid bilayers. Gramicidin and phospholipids were codispersed, after removal of the solvents chloroform/methanol or trifluoroethanol which resulted in nonchannel and channel conformations, respectively, as confirmed using circular dichroism (CD). The fluorescence emission maxima of the nonchannel form were shifted toward shorter wavelengths by heating at 60 degrees C (for 0-12 h), which converted it to a channel form, again as confirmed by CD. The channel form did not respond to heat treatment. Heat treatment also increased the fluorescence anisotropy of the nonchannel gramicidin tryptophans. The rate of transition from the nonchannel to channel conformation was found to be faster if phosphatidylethanolamine was present in combination with phosphatidylcholine compared to phosphatidylcholine alone. Also, gramicidin in bilayers of the polyunsaturated 1-palmitoyl-2-docosahexaenoyl-phosphatidylcholine converted more rapidly compared to 1-palmitoyl-2-oleoylphosphatidylcholine. Using the fluorescence anisotropy of the membrane lipid probe 1,6-diphenyl-1,3,5-hexatriene, it was also shown that the motional properties of the surrounding lipid acyl chains differed for the channel and nonchannel gramicidin conformations. The possibility that lipids tending to favor the hexagonal phase (HII) would enhance the rate of the nonchannel to channel transition was supported by 31P NMR which revealed the presence of some HII lipids in the channel preparations. The results of this study suggest that gramicidin may serve as a useful model for similar conformational transitions in other more complex membrane proteins.
Collapse
Affiliation(s)
- K J Cox
- Department of Pathology and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
| | | | | | | |
Collapse
|
7
|
Easton PL, Hinton JF, Newkirk DK. Kinetics of channel formation of gramicidins A and B in phospholipid vesicle membranes. Biophys J 1990; 57:63-9. [PMID: 1688716 PMCID: PMC1280643 DOI: 10.1016/s0006-3495(90)82507-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The thermal incorporation and channel formation of gramicidins A and B into phosphatidylcholine/phosphatidylglycerol large unilamellar vesicle membranes was studied using 23Na NMR. Delta H and delta S of activation for channel formation for gramicidin A are 11.8 kcal/mol and -11 e.u., respectively. For gramicidin B, delta H and delta S of activation are 14.6 kcal/mol and -4 e.u., respectively. Possible reasons for the differences in delta H and delta S of activation between the two analogues are discussed.
Collapse
Affiliation(s)
- P L Easton
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville 72701
| | | | | |
Collapse
|
8
|
Hinton JF, Fernandez JQ, Shungu DC, Whaley WL, Koeppe RE, Millett FS. TI-205 nuclear magnetic resonance determination of the thermodynamic parameters for the binding of monovalent cations to gramicidins A and C. Biophys J 1988; 54:527-33. [PMID: 2462930 PMCID: PMC1330351 DOI: 10.1016/s0006-3495(88)82985-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Thermodynamic parameters for the binding of the monovalent cations, Li+, Na+, K+, Rb+, Cs+, NH4+, TI+, and Ag+, to gramicidin A and for the binding of TI+ to gramicidin C, incorporated into lysophosphatidylcholine, have been determined using a combination of TI-205 nuclear magnetic resonance spectroscopy and competition binding. The thermodynamic parameters, enthalpy and entropy, are discussed in terms of a process involving the transfer of cations from an aqueous to amide environment.
Collapse
Affiliation(s)
- J F Hinton
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville 72701
| | | | | | | | | | | |
Collapse
|
9
|
LoGrasso PV, Moll F, Cross TA. Solvent history dependence of gramicidin A conformations in hydrated lipid bilayers. Biophys J 1988; 54:259-67. [PMID: 2462923 PMCID: PMC1330292 DOI: 10.1016/s0006-3495(88)82955-2] [Citation(s) in RCA: 90] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Reconstituted lipid bilayers of dimyristoylphosphatidylcholine (DMPC) and gramicidin A' have been prepared by cosolubilizing gramicidin and DMPC in one of three organic solvent systems followed by vacuum drying and hydration. The conformational state of gramicidin as characterized by 23Na NMR, circular dichroism, and solid state 15N NMR is dependent upon the cosolubilizing solvent system. In particular, two conformational states are described; a state in which Na+ has minimal interactions with the polypeptide, referred to as a nonchannel state, and a state in which Na+ interacts very strongly with the polypeptide, referred to as the channel state. Both of these conformations are intimately associated with the hydrophobic core of the lipid bilayer. Furthermore, both of these states are stable in the bilayer at neutral pH and at a temperature above the bilayer phase transition temperature. These results with gramicidin suggest that the conformation of membrane proteins may be dictated by the conformation before membrane insertion and may be dependent upon the mechanism by which the insertion is accomplished.
Collapse
Affiliation(s)
- P V LoGrasso
- Department of Chemistry, Florida State University, Tallahassee 32306-3006
| | | | | |
Collapse
|
10
|
Shungu DC, Hinton JF, Koeppe RE, Millett FS. Investigation of the interaction between thallous ions and gramicidin A in dimyristoylphosphatidylcholine vesicles: a thallium-205 NMR equilibrium study. Biochemistry 1986; 25:6103-8. [PMID: 2431708 DOI: 10.1021/bi00368a040] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
This study reports the first direct observation of multiple occupancy of the gramicidin A channel by Tl+ ions. 205Tl NMR has been used to study the equilibrium binding of Tl+ by gramicidin A incorporated in sonicated dimyristoylphosphatidylcholine vesicles. It is shown that only multiple-channel occupancy can account for the 205Tl chemical shifts measured. The data are analyzed to yield the equilibrium association constants of 450-600 and 5-20 M-1 for the binding of the first and the second ions at 34 degrees C, respectively.
Collapse
|
11
|
Hinton JF, Whaley WL, Shungu D, Koeppe RE, Millett FS. Equilibrium binding constants for the group I metal cations with gramicidin-A determined by competition studies and T1+-205 nuclear magnetic resonance spectroscopy. Biophys J 1986; 50:539-44. [PMID: 2428415 PMCID: PMC1329731 DOI: 10.1016/s0006-3495(86)83492-0] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The equilibrium binding constants of the Group I metal cations with gramicidin A in aqueous dispersions of lyso-PC have been determined using a combination of competitive binding with the T1+ ion and T1-205 NMR spectroscopy. The values of the binding constants at 34 degrees C are Li (32.2 M-1), Na (36.9 M-1), K (52.6 M-1), Rb (55.9 M-1), and Cs (54.0 M-1). The equilibrium binding constant for the T1+ ion at this temperature is 582 M-1. The relationships between the binding constants, the free energy of the binding process, and the cation selectivity of the gramicidin A channel are discussed.
Collapse
|
12
|
Hinton JF, Koeppe RE, Shungu D, Whaley WL, Paczkowski JA, Millett FS. Equilibrium binding constants for Tl+ with gramicidins A, B and C in a lysophosphatidylcholine environment determined by 205Tl nuclear magnetic resonance spectroscopy. Biophys J 1986; 49:571-7. [PMID: 2420383 PMCID: PMC1329498 DOI: 10.1016/s0006-3495(86)83668-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Nuclear Magnetic Resonance (NMR) 205Tl spectroscopy has been used to monitor the binding of Tl+ to gramicidins A, B, and C packaged in aqueous dispersions of lysophosphatidylcholine. For 5 mM gramicidin dimer in the presence of 100 mM lysophosphatidylcholine, only approximately 50% or less of the gramicidin appears to be accessible to Tl+. Analysis of the 205Tl chemical shift as a function of Tl+ concentration over the 0.65-50 mM range indicates that only one Tl+ ion can be bound by gramicidin A, B, or C under these experimental conditions. In this system, the Tl+ equilibrium binding constant is 582 +/- 20 M-1 for gramicidin 1949 +/- 100 M-1 for gramicidin B, and 390 +/- 20 M-1 for gramicidin C. Gramicidin B not only binds Tl+ more strongly but it is also in a different conformational state than that of A and C, as shown by Circular Dichroism spectroscopy. The 205Tl NMR technique can now be extended to determinations of binding constants of other cations to gramicidin by competition studies using a 205Tl probe.
Collapse
|
13
|
Spisni A, Pasquali-Ronchetti I, Casali E, Lindner L, Cavatorta P, Masotti L, Urry DW. Supramolecular organization of lysophosphatidylcholine-packaged Gramicidin A. BIOCHIMICA ET BIOPHYSICA ACTA 1983; 732:58-68. [PMID: 6191773 DOI: 10.1016/0005-2736(83)90186-4] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Heat derived gramicidin A'/L-alpha-lysophosphatidylcholine complexes were separated on a sucrose gradient to form two fractions: Fraction A which had an approximately constant Gramicidin A' to phospholipid ratio of 8 to 10 lipid molecules per Gramicidin A' molecule and Fraction B which had a larger but variable ratio. Fluorescence and circular dichroism studies confirmed Fraction A to be a lipid-incorporated channel state. Electron microscopic studies, using uranyl acetate negative staining, showed fraction A to be a membranous state with the formation of bilayer vesicles, that is, the interaction of peptide and phospholipid micelles causes the lipid to reorganize into a bilayer structure. Freeze-fracture replicas of the channel incorporated state demonstrated the presence of a supramolecular organization of particles exhibiting a tendency to form rows with a 50-60 A periodicity along the row and with 70-80 A distance between rows. An idealized working model for the incorporated state is presented.
Collapse
|
14
|
Cavatorta P, Spisni A, Casali E, Lindner L, Masotti L, Urry DW. Intermolecular interactions of gramicidin A' transmembrane channels incorporated into lysophosphatidylcholine lipid systems. BIOCHIMICA ET BIOPHYSICA ACTA 1982; 689:113-20. [PMID: 6179540 DOI: 10.1016/0005-2736(82)90195-x] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Fluorescence studies are reported on gramicidin A' incorporated into lysophosphatidylcholine phospholipid structures. The shift in the emission maximum during incorporation and the quenching of fluorescence by I- and by acrylamide of the incorporated state obtained after prolonged heating are consistent with the presence of the channel state comprised of two single-stranded beta 6 -helices associated head-to-head (formyl end-to-formyl end). The quantum yield for the incorporated state, when gramicidin A' is within the lipid matrix, is very low and indicates the occurrence of intermolecular Trp-Trp interactions. Possible interactions between channels within the lipid matrix are discussed utilizing Trp-Trp contacts.
Collapse
|