How proteins adapt to a membrane–water interface

Killian, J. Antoinette; Heijne, Gunnar von

doi:10.1016/s0968-0004(00)01626-1

Cited by 667 publications

(615 citation statements)

References 30 publications

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“…Implication for Membrane Proteins-Although Trp often is considered to be hydrophobic, Trp residues have long been described as "anchoring" residues in membrane proteins (2,4,5), and as early as 1984, it was found, using [Trp 1 ]gA channels, that there is a significant penalty associated with burying Trp residues in the bilayer core (62). More recently, it was shown that Trps near the C terminus of a membrane-spanning ␣-helix display a distinctly different behavior from those near the N terminus, reflected in large differences in the allowed side chain torsion angles and ring motions, highlighting the directionality of an ␣-helix relative to the bilayer/solution interface (67).…”

Section: Discussionmentioning

confidence: 99%

“…Some insights have been gained by examining free indole analogues in lipid bilayer environments, where NMR investigations led to the suggestion that aromaticity and ring shape are significant factors for the preference of Trp for the polar/nonpolar interface (10,11). It is unclear, nevertheless, to what extent these and other (12) experiments with small indole analogues, which were not "anchored" by a peptide chain possessing secondary structure, represent the situation in the transmembrane region of a bilayer-spanning protein (4).…”

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confidence: 99%

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The Preference of Tryptophan for Membrane Interfaces

Sun

Greathouse

Andersen

et al. 2008

Journal of Biological Chemistry

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To better understand the structural and functional roles of tryptophan at the membrane/water interface in membrane proteins, we examined the structural and functional consequences of Trp 3 1-methyl-tryptophan substitutions in membranespanning gramicidin A channels. Gramicidin A channels are miniproteins that are anchored to the interface by four Trps near the C terminus of each subunit in a membrane-spanning dimer. We masked the hydrogen bonding ability of individual or multiple Trps by 1-methylation of the indole ring and examined the structural and functional changes using circular dichroism spectroscopy, size exclusion chromatography, solid state 2 H NMR spectroscopy, and single channel analysis. N-Methylation causes distinct changes in the subunit conformational preference, channel-forming propensity, single channel conductance and lifetime, and average indole ring orientations within the membrane-spanning channels. The extent of the local ring dynamic wobble does not increase, and may decrease slightly, when the indole NH is replaced by the non-hydrogen-bonding and more bulky and hydrophobic N-CH 3 group. The changes in conformational preference, which are associated with a shift in the distribution of the aromatic residues across the bilayer, are similar to those observed previously with Trp 3 Phe substitutions. We conclude that indole N-H hydrogen bonding is of major importance for the folding of gramicidin channels. The changes in ion permeability, however, are quite different for Trp 3 Phe and Trp 3 1-methyl-tryptophan substitutions, indicating that the indole dipole moment and perhaps also ring size and are important for ion permeation through these channels.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

The Preference of Tryptophan for Membrane Interfaces

Sun

Greathouse

Andersen

et al. 2008

Journal of Biological Chemistry

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“…The tryptophans are conserved between many homologues including the yeast protein Snc2p (Figure 1) for which no tryptophan-based inhibition was observed (Chen et al, 2004). In fact, tryptophan residues are found in many single-spanning membrane proteins near the membrane-water interface where they belong to characteristic belts containing both basic and aromatic residues (Killian and von Heijne, 2000). The positively charged residues are known to contact the phospholipids head groups, whereas the polar-aromatic residues penetrate into a region near the lipid carbonyl chain.…”

Section: Discussionmentioning

confidence: 99%

Determinants of Synaptobrevin Regulation in Membranes

Siddiqui

Vites

Stein³

et al. 2007

MBoC

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Neuronal exocytosis is driven by the formation of SNARE complexes between synaptobrevin 2 on synaptic vesicles and SNAP-25/syntaxin 1 on the plasma membrane. It has remained controversial, however, whether SNAREs are constitutively active or whether they are down-regulated until fusion is triggered. We now show that synaptobrevin in proteoliposomes as well as in purified synaptic vesicles is constitutively active. Potential regulators such as calmodulin or synaptophysin do not affect SNARE activity. Substitution or deletion of residues in the linker connecting the SNARE motif and transmembrane region did not alter the kinetics of SNARE complex assembly or of SNARE-mediated fusion of liposomes. Remarkably, deletion of C-terminal residues of the SNARE motif strongly reduced fusion activity, although the overall stability of the complexes was not affected. We conclude that although complete zippering of the SNARE complex is essential for membrane fusion, the structure of the adjacent linker domain is less critical, suggesting that complete SNARE complex assembly not only connects membranes but also drives fusion. INTRODUCTIONCommunication between neurons is mediated by neurotransmitters that are released from presynaptic nerve endings by Ca 2ϩ -dependent exocytosis of synaptic vesicles. Exocytotic fusion of the vesicle with the synaptic plasma membrane is mediated by the proteins synaptobrevin 2/VAMP2, SNAP-25, and syntaxin 1 (Jahn and Scheller, 2006;Rizo et al., 2006). These proteins are members of the SNARE protein family that are involved in all fusion events of the secretory pathway. SNAREs are characterized by stretches of 60-70 amino acids arranged in heptad repeats, termed SNARE motifs (Weimbs et al., 1997;Fasshauer et al., 1998b;Bock et al., 2001;Day et al., 2006). Syntaxin and synaptobrevin each contain a single SNARE motif that is located adjacent to a C-terminal transmembrane domain. In contrast, SNAP-25 contains two SNARE motifs connected by a palmitoylated linker region that serves as membrane anchor.Synaptobrevin resides in synaptic vesicles, whereas SNAP-25 and syntaxin 1 reside in the plasma membrane. The SNARE motifs of syntaxin, SNAP-25, and synaptobrevin readily assemble into quarternary bundles of ␣-helices (Fasshauer et al., 1997;Sutton et al., 1998). Assembly would thus lead to a tight connection between the membranes. According to this view, assembly is nucleated at the Nterminal ends of the SNARE-motifs and proceeds toward the C-terminal membrane anchor ("zippering"), resulting in a strained "trans"-complex . During membrane merger, the trans-complex would relax into a "cis"-complex in which the transmembrane domains are aligned in parallel. To regenerate the SNAREs for another round of fusion, SNARE complexes need to be disassembled by the AAAϩ-ATPase NEM-sensitive factor (NSF) in conjunction with cofactors termed soluble NSF attachment proteins (SNAPs; Sollner et al., 1993).Although the "zippering" hypothesis of SNARE function has received a lot of experimental support, it is still unclear...

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“…Alternatively, the location of the tryptophan could be different for melittin bound to various micelles. Tryptophan residues in membrane peptides and proteins are known to be preferentially localized at the membrane interfacial region (Killian and von Heijne 2000). In a micellar environment, however, the thermal thickness of the interfacial region is less.…”

Section: Discussionmentioning

confidence: 99%

Effect of micellar charge on the conformation and dynamics of melittin

Raghuraman

Chattopadhyay

2004

Eur Biophys J

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Electrostatic interactions play a crucial role in modulating and stabilizing molecular interactions in membranes and membrane-mimetic systems such as micelles. We have monitored the change in the conformation and dynamics of the cationic hemolytic peptide melittin bound to micelles of various charge types, utilizing fluorescence and circular dichroism (CD) spectroscopy. The sole tryptophan of melittin displays a red-edge excitation shift (REES) of 3-6 nm when bound to anionic, nonionic, and zwitterionic micelles. This suggests that melittin is localized in a restricted environment, probably in the interfacial region of the micelles, and this region offers considerable restriction to the reorientational motion of the solvent dipoles around the excited state tryptophan in melittin. Further, the rotational mobility of melittin is considerably reduced in these micelles and is found to be dependent on the surface charge of micelles. Interestingly, our results show that melittin does not partition into cetyltrimethylammonium bromide (CTAB) micelles owing to electrostatic repulsion between melittin and CTAB micelles, both of which carry a positive charge. In addition, the fluorescence lifetime of melittin is modulated in micelles of different charge types. The lowest mean fluorescence lifetime is observed in the case of melittin bound to anionic sodium dodecyl sulfate (SDS) micelles. CD spectroscopy shows that micelles induce significant helicity to melittin, with maximum helicity being induced in the case of melittin bound to SDS micelles. Fluorescence quenching measurements using the neutral aqueous quencher acrylamide show differential accessibility of melittin in various types of micelles. Taken together, our results show that micellar surface charge can modulate the conformation and dynamics of melittin. These results could be relevant to understanding the role of the surface charge of membranes in the interaction of membrane-active, amphiphilic peptides with membranes.

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How proteins adapt to a membrane–water interface

Cited by 667 publications

References 30 publications

The Preference of Tryptophan for Membrane Interfaces

The Preference of Tryptophan for Membrane Interfaces

Determinants of Synaptobrevin Regulation in Membranes

Effect of micellar charge on the conformation and dynamics of melittin

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