Binding of Molten Globule-like Conformations to Lipid Bilayers

Bañuelos, Sonia; Muga, Arturo

doi:10.1074/jbc.270.50.29910

Cited by 114 publications

(32 citation statements)

References 37 publications

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“…It was shown that α-LA also interacts with membranes containing negatively charged lipids such as phosphatidylglycerol. Interactions of several conformers of α-LA in aqueous solution with negatively charged large unilamellar vesicles (lecithin, 1,2-dioleoylphosphatidylglycerol, dipalmitoylphosphatidyl-glycerol,) were studied by CD, infrared spectroscopy, differential scanning calorimetry, and by content leakage experiments [ 205 , 206 , 207 ].…”

Section: Interactions Of α-Lactalbumin With Membranes and Hydrophmentioning

confidence: 99%

“…Studies of interactions of α-LA with large unilamellar vesicles (lecithin, 1,2-dioleoylphosphatidylglycerol, dipalmitoylphosphatidylglycerol,) by CD, infrared spectroscopy, differential scanning calorimetry, and by content leakage experiments showed that the affinity of α-LA for negatively charged vesicles strongly depends on the conformational properties of the protein in solution and the native-like, calcium-bound, ordered conformations associate with bilayer through electrostatic interactions [ 205 , 206 , 207 ]. Ca 2+ -α-LA perturbs the membranes significantly only at pH 4.5, i.e., below the isoelectric point (pI) of the protein.…”

Section: Interactions Of α-Lactalbumin With Membranes and Hydrophmentioning

confidence: 99%

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α-Lactalbumin, Amazing Calcium-Binding Protein

Permyakov

2020

Biomolecules

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α-Lactalbumin (α-LA) is a small (Mr 14,200), acidic (pI 4–5), Ca2+-binding protein. α-LA is a regulatory component of lactose synthase enzyme system functioning in the lactating mammary gland. The protein possesses a single strong Ca2+-binding site, which can also bind Mg2+, Mn2+, Na+, K+, and some other metal cations. It contains several distinct Zn2+-binding sites. Physical properties of α-LA strongly depend on the occupation of its metal binding sites by metal ions. In the absence of bound metal ions, α-LA is in the molten globule-like state. The binding of metal ions, and especially of Ca2+, increases stability of α-LA against the action of heat, various denaturing agents and proteases, while the binding of Zn2+ to the Ca2+-loaded protein decreases its stability and causes its aggregation. At pH 2, the protein is in the classical molten globule state. α-LA can associate with membranes at neutral or slightly acidic pH at physiological temperatures. Depending on external conditions, α-LA can form amyloid fibrils, amorphous aggregates, nanoparticles, and nanotubes. Some of these aggregated states of α-LA can be used in practical applications such as drug delivery to tissues and organs. α-LA and some of its fragments possess bactericidal and antiviral activities. Complexes of partially unfolded α-LA with oleic acid are cytotoxic to various tumor and bacterial cells. α-LA in the cytotoxic complexes plays a role of a delivery carrier of cytotoxic fatty acid molecules into tumor and bacterial cells across the cell membrane. Perhaps in the future the complexes of α-LA with oleic acid will be used for development of new anti-cancer drugs.

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Section: Interactions Of α-Lactalbumin With Membranes and Hydrophmentioning

confidence: 99%

Section: Interactions Of α-Lactalbumin With Membranes and Hydrophmentioning

confidence: 99%

α-Lactalbumin, Amazing Calcium-Binding Protein

Permyakov

2020

Biomolecules

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“…Artificial membranes may thus be useful to specifically address how HAMLET interacts with lipid bilayers. The protein constituent of HAMLET, HLA, is a 14.2-kDa milk protein known to interact with different lipid membranes, with partially unfolded states like molten globules having increased affinity for lipid bilayers [9], [10], [11], [12]. Native, folded HLA alone is not efficiently internalized by tumor cells and has no effect on cell viability.…”

Section: Introductionmentioning

confidence: 99%

HAMLET Interacts with Lipid Membranes and Perturbs Their Structure and Integrity

et al. 2010

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BackgroundCell membrane interactions rely on lipid bilayer constituents and molecules inserted within the membrane, including specific receptors. HAMLET (human α-lactalbumin made lethal to tumor cells) is a tumoricidal complex of partially unfolded α-lactalbumin (HLA) and oleic acid that is internalized by tumor cells, suggesting that interactions with the phospholipid bilayer and/or specific receptors may be essential for the tumoricidal effect. This study examined whether HAMLET interacts with artificial membranes and alters membrane structure.Methodology/Principal FindingsWe show by surface plasmon resonance that HAMLET binds with high affinity to surface adherent, unilamellar vesicles of lipids with varying acyl chain composition and net charge. Fluorescence imaging revealed that HAMLET accumulates in membranes of vesicles and perturbs their structure, resulting in increased membrane fluidity. Furthermore, HAMLET disrupted membrane integrity at neutral pH and physiological conditions, as shown by fluorophore leakage experiments. These effects did not occur with either native HLA or a constitutively unfolded Cys-Ala HLA mutant (rHLAall-Ala). HAMLET also bound to plasma membrane vesicles formed from intact tumor cells, with accumulation in certain membrane areas, but the complex was not internalized by these vesicles or by the synthetic membrane vesicles.Conclusions/SignificanceThe results illustrate the difference in membrane affinity between the fatty acid bound and fatty acid free forms of partially unfolded HLA and suggest that HAMLET engages membranes by a mechanism requiring both the protein and the fatty acid. Furthermore, HAMLET binding alters the morphology of the membrane and compromises its integrity, suggesting that membrane perturbation could be an initial step in inducing cell death.

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“…Lactalbumin (8), retinol binding protein (38), colicin A (7), diphtheria toxin T-domain (5), StAR lipid binding domains (10), and barley nsLTP (12) are a few such proteins. The GLTP-fold represents both a novel motif among lipid binding/transfer proteins and a novel membrane interaction motif among amphitropic peripheral proteins that translocate to membranes during function (25).…”

Section: Discussionmentioning

confidence: 99%

Conformational Folding and Stability of the HET-C2 Glycolipid Transfer Protein Fold: Does a Molten Globule-like State Regulate Activity?

et al. 2011

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The glycolipid transfer protein (GLTP) superfamily is defined by the human GLTP-fold which represents a novel motif for lipid binding/transfer and for reversible interaction with membranes, i.e. peripheral amphitropic proteins. Despite limited sequence homology with human GLTP, we recently showed that HET-C2 GLTP of Podospora anserina is organized conformationally as a GLTP-fold. Currently, insights into the folding stability and conformational states that regulate GLTP-fold activity are almost nonexistent. To gain such insights into the disulfide-less GLTP-fold, we investigated the effect of changing pH on the fungal HET-C2 GLTP-fold by taking advantage of its two tryptophans and four tyrosines (compared to three tryptophans and ten tyrosines in human GLTP). pH-Induced conformational alterations were determined by changes in: i) intrinsic tryptophan fluorescence (intensity, emission wavelength maximum, anisotropy); ii) circular dichroism over the near-UV and far-UV ranges including thermal stability profiles of the derivatized molar ellipticity at 222 nm; iii) fluorescence properties of 1-anilinonaphthalene-8-sulfonic acid; iv) glycolipid inter-membrane transfer activity monitored by Förster resonance energy transfer. Analyses of our recently solved crystallographic structure of HET-C2 (1.9 Å) enabled identification of side chain electrostatic interactions that contribute to HET-C2 GLTP-fold stability and can be altered by pH change. Side-chain interactions include numerous salt bridges and interchain cation-pi interactions, but not intramolecular disulfide bridges. Histidine residues are especially important for stabilizing the local positioning of the two tryptophan residues and the conformation of adjacent chains. Induction of a low pH-induced, molten globule-like state inhibited glycolipid intermembrane transfer by the HET-C2 GLTP-fold.

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Binding of Molten Globule-like Conformations to Lipid Bilayers

Cited by 114 publications

References 37 publications

α-Lactalbumin, Amazing Calcium-Binding Protein

α-Lactalbumin, Amazing Calcium-Binding Protein

HAMLET Interacts with Lipid Membranes and Perturbs Their Structure and Integrity

Conformational Folding and Stability of the HET-C2 Glycolipid Transfer Protein Fold: Does a Molten Globule-like State Regulate Activity?

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