Gramicidin A analogs: influence of the substitution of the tryptophans by naphthylalanines

Daumas, P.; Heitz, Fréderic; Ranjalahy-Rasoloarijao, L.; Lázaro, R.

doi:10.1016/0300-9084(89)90135-1

Cited by 32 publications

(28 citation statements)

References 9 publications

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“…Gramicidin has proved to be a powerful model for elucidating the role of tryptophan at the membrane-water interface for maintaining ion channel structure and assembly [16,17, 32–37]. The tryptophan residues in gramicidin channels have previously been shown to be crucial for the structure and function of the ion channel [16,17,32–35].…”

Section: Introductionmentioning

confidence: 99%

“…The tryptophan residues in gramicidin channels have previously been shown to be crucial for the structure and function of the ion channel [16,17,32–35]. The importance of tryptophans is apparent from previous observations that the cation conductivity of the channel is reduced upon substitution of one or all of the tryptophan residues by phenylalanine, tyrosine or naphthylalanine [16,17,32], and also upon ultraviolet irradiation or chemical modification of the tryptophans [35,38,39]. It has been previously shown that gramicidins with Trp → Phe or Tyr substitutions have greater difficulty in forming membrane-spanning dimeric channels [16,35].…”

Section: Introductionmentioning

confidence: 99%

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Importance of indole NH hydrogen bonding in the organization and dynamics of gramicidin channels

Chaudhuri

Haldar

Sun

et al. 2014

Biochimica et Biophysica Acta (BBA) - Biomembranes

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The linear ion channel peptide gramicidin represents an excellent model for exploring the principles underlying membrane protein structure and function, especially with respect to tryptophan residues. The tryptophan residues in gramicidin channels are crucial for the structure and function of the channel. In order to test the importance of indole hydrogen bonding for the biophysical properties of gramicidin channels, we monitored the effect of N-methylation of gramicidin tryptophans, using a combination of steady state and time-resolved fluorescence approaches along with circular dichroism spectroscopy. We show here that in the absence of hydrogen bonding ability of tryptophans, tetramethyltryptophan gramicidin (TM-gramicidin) is unable to maintain the single stranded, head-to-head dimeric channel conformation in membranes. Our results show that TM-gramicidin displays a red-shifted fluorescence emission maximum, lower red edge excitation shift (REES), and higher fluorescence intensity and lifetime, consistent with its nonchannel conformation. This is in agreement with the measured location (average depth) of the 1-methyltryptophans in TM-gramicidin using the parallax method. These results bring out the usefulness of 1-methyltryptophan as a fluorescent tool to examine the hydrogen bonding ability of tryptophans in proteins and peptides. We conclude that changes in the hydrogen bonding ability of tryptophans, along with coupled changes in peptide backbone structure induce the loss of single stranded β6.3 helical dimer conformation. These results agree with earlier results from size-exclusion chromatography and single-channel measurements for TM-gramicidin, and confirm the importance of indole hydrogen bonding for the conformation and function of ion channels and membrane proteins.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Importance of indole NH hydrogen bonding in the organization and dynamics of gramicidin channels

Chaudhuri

Haldar

Sun

et al. 2014

Biochimica et Biophysica Acta (BBA) - Biomembranes

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“…Tryptophan residue substitution on gA by phenylalanine (gM), tyrosine (gT), or naphthylalanine (gN) results in a decrease in channel conductivity [30][31][32]. In addition, UV irradiation or chemical modification of the Trp side chains have been shown to induce comparable changes in the gA channel conductivity [21,33].…”

Section: Discussionmentioning

confidence: 99%

A fluorescence approach of the gamma radiation effects on gramicidin A inserted in liposomes

Nae

Gazdaru

Acasandrei

et al. 2008

Journal of Peptide Science

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The fluorescence of tryptophan residues of gramicidin A (gA), bound to phosphatidylcholine liposomes contains valuable information about local changes in the environment of the molecule induced by gamma radiation. With this work, we aim to demonstrate that the gamma radiation effect on the peptide involves the action of free radicals, derived from water radiolysis and the process of lipid peroxidation. Basically, the methodology consists of the analysis of UV and fluorescence emission spectra of the peptide liposome complexes under control conditions and upon gamma irradiation. Free radical production was impaired by the removal of molecular oxygen or the presence of ethanol in the liposome suspension. The intensity of the tryptophan fluorescence was recorded as a function of the gamma radiation dose in the range of 0-250 Gy and the data were fitted with a single decay exponential function containing an additional constant term (named residual fluorescence). The correlation between the decrease in tryptophan fluorescence emission (D(c) = 80 +/- 10 Gy) and increase in gamma radiation dose indicates the partial damage of the tryptophan side chains of gA. O(2) removal or ethanol addition partially reduced the decay of the tryptophan fluorescence emission involving an indirect action of gamma radiation via a water radiolysis mechanism. The residual fluorescence emission (A(0)) increases in O(2)-free buffer (98 +/- 13) and in 10% ethanol-containing buffer (74 +/- 34) compared to control conditions (23 +/- 5). Varying the dose rate between 1-10 Gy/min at a constant dose of 50 Gy, an inverse dose-rate effect was observed. Thus, our study provides evidence for the lipid peroxidation effect on the tryptophan fluorescence. In conclusion, this article sustains the hypothesis of the connection between the lipid peroxidation and structural changes of membrane proteins induced by gamma radiation.

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“…The significance of such organization in terms of functioning of the channel is brought out by the fact that substitution, photodamage, or chemical modification of these tryptophans are known to give rise to channels with altered conformation and reduced conductivity. 60,66,[159][160][161][162][163] More importantly, REES and related fluorescence approaches have been used to distinguish between the channel and non-channel conformations of gramicidin in membranes. 156 REES of gramicidin is therefore sensitive to the conformation adopted by the peptide in the membrane.…”

Section: Monitoring Protein Structure and Dynamics By Rees 209mentioning

confidence: 99%

Novel Insights Into Protein Structure and Dynamics Utilizing the Red Edge Excitation Shift Approach

Raghuraman

Kelkar

Chattopadhyay

Reviews in Fluorescence 2005

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A shift in the wavelength of maximum fluorescence emission toward higher wavelengths, caused by a corresponding shift in the excitation wavelength toward the red edge of the absorption band, is termed the red edge excitation shift (REES). This effect is mostly observed with polar fluorophores in motionally restricted media such as viscous solutions or condensed phases where the dipolar relaxation time for the solvent shell around a fluorophore is comparable to or longer than its fluorescence lifetime. REES arises from slow rates of solvent relaxation (reorientation) around an excited state fluorophore which depends on the motional restriction imposed on the solvent molecules in the immediate vicinity of the fluorophore. Utilizing this approach, it becomes possible to probe the mobility parameters of the environment itself (which is represented by the relaxing solvent molecules) using the fluorophore merely as a reporter group. Further, since the ubiquitous solvent for biological systems is water, the information obtained in such cases will come from the otherwise 'optically silent' water molecules. This makes REES extremely useful since hydration plays a crucial modulatory role in the formation and maintenance of organized molecular assemblies such as folded proteins in aqueous solutions and biological membranes. The application of REES as a powerful tool to monitor the organization and dynamics of a variety of soluble, cytoskeletal, and membrane-bound proteins is discussed.

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Gramicidin A analogs: influence of the substitution of the tryptophans by naphthylalanines

Cited by 32 publications

References 9 publications

Importance of indole NH hydrogen bonding in the organization and dynamics of gramicidin channels

Importance of indole NH hydrogen bonding in the organization and dynamics of gramicidin channels

A fluorescence approach of the gamma radiation effects on gramicidin A inserted in liposomes

Novel Insights Into Protein Structure and Dynamics Utilizing the Red Edge Excitation Shift Approach

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