The Thermal Structural Transition of Alpha-Crystallin Modulates Subunit Interactions and Increases Protein Solubility

Maulucci, Giuseppe; Spirito, Marco De; Arcòvito, Giuseppe; Papi, Massimiliano

doi:10.1371/journal.pone.0030705

Cited by 6 publications

(2 citation statements)

References 34 publications

(54 reference statements)

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“…[65] also determined the phase transition temperature of the quaternary structure of this sHSP using static and dynamic light scattering measurements and found that it had a quaternary structural transition at 45°C [65]. The S52P mutation shifted the T m value as obtained from the temperature dependence curve of fraction unfolded (a U ) from 61 to 54°C ( Fig.…”

Section: Resultsmentioning

confidence: 99%

“…FT-IR spectroscopy, CD and differential scanning calorimetry studies revealed that a-crystallin had a phase change transition temperature between 60 and 62°C [64]. Maulucci et al [65] also determined the phase transition temperature of the quaternary structure of this sHSP using static and dynamic light scattering measurements and found that it had a quaternary structural transition at 45°C [65]. The S52P mutation shifted the T m value as obtained from the temperature dependence curve of fraction unfolded (a U ) from 61 to 54°C (Fig.…”

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A S52P mutation in the ‘α‐crystallin domain’ of Mycobacterium leprae HSP18 reduces its oligomeric size and chaperone function

et al. 2013

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Mycobacterium leprae HSP18 is a small heat shock protein (sHSP). It is a major immunodominant antigen of M. leprae pathogen. Previously, we have reported the existence of two M. leprae HSP18 variants in various leprotic patients. One of the variants has serine at position 52, whereas the other one has proline at the same position. We have also reported that HSP18 having proline at position 52 ( HSP18P 52 ) is a nonameric protein and exhibits chaperone function. However, the structural and functional characterization of wild-type HSP18 having serine at position 52 ( HSP18S 52 ) is yet to be explored. Furthermore, the implications of the S52P mutation on the structure and chaperone function of HSP18 are not well understood. Therefore, we cloned and purified these two HSP18 variants. We found that HSP18S 52 is also a molecular chaperone and an oligomeric protein. Intrinsic tryptophan fluorescence and far-UV CD measurements revealed that the S52P mutation altered the tertiary and secondary structure of HSP18. This point mutation also reduced the oligomeric assembly and decreased the surface hydrophobicity of HSP18, as revealed by HPLC and 4,4′-dianilino-1,1′-binaphthyl-5,5′-disulfonic acid binding studies, respectively. Mutant protein was less stable against thermal and chemical denaturation and was more susceptible towards tryptic cleavage than wild-type HSP18. HSP18P 52 had lower chaperone function and was less effective in protecting thermal killing of Escherichia coli than HSP18S 52. Taken together, our data suggest that serine 52 is important for the larger oligomerization and chaperone function of HSP18. Because both variants differ in stability and function, they may have different roles in the survival of M. leprae in infected hosts. Abbreviations ACD, a-crystallin domain; bis-ANS, 4,4′-dianilino-1,1′-binaphthyl-5,5′-disulfonic acid, dipotassium salt; CFU, colony-forming unit; FRET, F€ orster resonance energy transfer; Gu-HCl, guanidine hydrochloride; IPTG, isopropyl thio-b-D-galactoside; MDH, malate dehydrogenase; sHSP, small heat shock protein. Structured digital abstract

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A S52P mutation in the ‘α‐crystallin domain’ of Mycobacterium leprae HSP18 reduces its oligomeric size and chaperone function

et al. 2013

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α‐Crystallin Modulates its Chaperone Activity by Varying the Exposed Surface

et al. 2013

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The α-crystallin family of small heat shock proteins possesses chaperone activity in response to stress and is involved in several neurological, muscular, and ophthalmic pathologies. This family includes the vertebrate lens protein α-crystallin, associated with cataract disease. In this study, by combining small-angle X-ray and light scattering techniques, the structure and shape of α-crystallin was revealed in its native state and after a transition caused by heat stress. Below critical temperature (Tc ), α-crystallin appears as an ellipsoid with a central cavity; whereas at high temperatures the cavity almost disappears, and the protein rearranges its structure, increasing the solvent-exposed surface while retaining the ellipsoidal symmetry. Contextually, at Tc , α-crystallin chaperone binding shows an abrupt increase. By modelling the chaperone activity as the formation of a complex composed of α-crystallin and an aggregating substrate, it was demonstrated that the increase of α-crystallin-exposed surface is directly responsible for its gain in chaperone functionality.

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Observation of a crossover in kinetic aggregation of Palladium colloids

Ghafari

Ranjbar

Rouhani

2015

Applied Surface Science

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We use field emission scanning electron microscope (FE-SEM) to investigate the growth of palladium colloids over the surface of thin films of WO3/glass. The film is prepared by Pulsed Laser Deposition (PLD) at different temperatures. A PdCl2 (aq) droplet is injected on the surface and in the presence of steam hydrogen the droplet is dried through a reduction reaction process. Two distinct aggregation regimes of palladium colloids are observed over the substrates. We argue that the change in aggregation dynamics emerges when the measured water drop Contact Angel (CA) for the WO3/glass thin films passes a certain threshold value, namely CA = 46 degrees, where a crossover in kinetic aggregation of palladium colloids occurs. Our results suggest that the mass fractal dimension of palladium aggregates follows a power-law behavior. The fractal dimension (Df) in the fast aggregation regime, where the measured CA values vary from 27 up to 46 degrees, according to different substrate deposition temperatures, is Df = 1.75 (0.02). This value of Df is in excellent agreement with kinetic aggregation of other colloidal systems in fast aggregation regime. Whereas for the slow aggregation regime, with CA = 58 degrees, the fractal dimension changes abruptly to Df=1.92 (0.03). We have also used a modified Box-Counting method to calculate fractal dimension of gray-level images and observe that the crossover at around CA = 46 degrees remains unchanged.Comment: 13 pages, 8 figure

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The Thermal Structural Transition of Alpha-Crystallin Modulates Subunit Interactions and Increases Protein Solubility

Cited by 6 publications

References 34 publications

A S52P mutation in the ‘α‐crystallin domain’ of Mycobacterium leprae HSP18 reduces its oligomeric size and chaperone function

A S52P mutation in the ‘α‐crystallin domain’ of Mycobacterium leprae HSP18 reduces its oligomeric size and chaperone function

α‐Crystallin Modulates its Chaperone Activity by Varying the Exposed Surface

Observation of a crossover in kinetic aggregation of Palladium colloids

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