<i>Phytolacca americana</i> lectin (Pa-2; pokeweed mitogen): an intrinsically unordered protein and its conversion into partial order at low pH

Ahmad, Ejaz; Rahman, Shah Kamranur; Khan, Javed Masood; Varshney, A. K.; Khan, Rizwan Hasan

doi:10.1042/bsr20090035

Cited by 14 publications

(5 citation statements)

References 39 publications

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“…The intrinsic spectra were recorded between 300 to 400 nm with excitation wavelength of 295 nm. For light scattering measurements, the excitation and emission wavelength was set at 350 nm as used in our previous report [22]. Both the excitation and emission slit widths were set at 5 nm.…”

Section: Methodsmentioning

confidence: 99%

Monomeric Banana Lectin at Acidic pH Overrules Conformational Stability of Its Native Dimeric Form

et al. 2013

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Banana lectin (BL) is a homodimeric protein categorized among jacalin-related family of lectins. The effect of acidic pH was examined on conformational stability of BL by using circular dichroism, intrinsic fluorescence, 1-anilino-8-napthalene sulfonate (ANS) binding, size exclusion chromatography (SEC) and dynamic light scattering (DLS). During acid denaturation of BL, the monomerization of native dimeric protein was found at pH 2.0. The elution profile from SEC showed two different peaks (59.65 ml & 87.98 ml) at pH 2.0 while single peak (61.45 ml) at pH 7.4. The hydrodynamic radii (R h) of native BL was 2.9 nm while at pH 2.0 two species were found with R h of 1.7 and 3.7 nm. Furthermore at, pH 2.0 the secondary structures of BL remained unaltered while tertiary structure was significantly disrupted with the exposure of hydrophobic clusters confirming the existence of molten globule like state. The unfolding of BL with different subunit status was further evaluated by urea and temperature mediated denaturation to check their stability. As inferred from high Cm and ΔG values, the monomeric form of BL offers more resistance towards chemical denaturation than the native dimeric form. Besides, dimeric BL exhibited a Tm of 77°C while no loss in secondary structures was observed in monomers even up to 95°C. To the best of our knowledge, this is the first report on monomeric subunit of lectins showing more stability against denaturants than its native dimeric state.

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Section: Methodsmentioning

confidence: 99%

Monomeric Banana Lectin at Acidic pH Overrules Conformational Stability of Its Native Dimeric Form

et al. 2013

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“…DG u varies linearly as a function of pH with a proportionality factor m. Extrapolation of the extreme back to the pH value where the maximum folded population exists gives an estimate of the value of DG u under that pH value, DG Hþ u [17]. The difference in free energy between the folded and unfolded states, DG u , was calculated by the following equation:…”

Section: Data Analysis Of Protein Denaturationmentioning

confidence: 99%

pH-Dependent Conformational Transitions in Conalbumin (Ovotransferrin), a Metalloproteinase from Hen Egg White

Rabbani

Ahmad

Zaidi

et al. 2011

Cell Biochem Biophys

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Acid unfolding pathway of conalbumin (CA), a monomeric glycoprotein from hen egg white, has been investigated using far- and near-UV CD spectroscopy, intrinsic fluorescence emission, extrinsic fluorescence probe 1-anilino-8-napthalene sulfonate (ANS) and dynamic light scattering (DLS). We observe pH-dependent changes in secondary and tertiary structure of CA. It has native-like α-helical secondary structure at pH 4.0 but loss structure at pH 3.0. The CA existed exclusively as a pre-molten globule state and molten globule state in solution at pH 4.0 and pH 3.0, respectively. The effect of pH on the conformation and thermostability of CA points toward its heat resistance at neutral pH. DLS results show that MG state existed as compact form in aqueous solutions with hydrodynamic radii of 4.7 nm. Quenching of tryptophan fluorescence by acrylamide further confirmed the accumulation of an intermediate state, partly unfolded, in-between native and unfolded states.

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“…Changes in pH can induce partial folding of intrinsically disordered proteins due to the minimization of their large net charge at neutral pH, decrease of charge/charge intramolecular repulsion and the hydrophobic-driven collapse (Ahmad et al, 2010). Our results showed that the decrease in pH did not promote structural changes on the C124 structure.…”

Section: Resultsmentioning

confidence: 99%

Charge neutralization as the major factor for the assembly of nucleocapsid-like particles from C-terminal truncated hepatitis C virus core protein

Souza

Lima

Braga

et al. 2016

PeerJ

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BackgroundHepatitis C virus (HCV) core protein, in addition to its structural role to form the nucleocapsid assembly, plays a critical role in HCV pathogenesis by interfering in several cellular processes, including microRNA and mRNA homeostasis. The C-terminal truncated HCV core protein (C124) is intrinsically unstructured in solution and is able to interact with unspecific nucleic acids, in the micromolar range, and to assemble into nucleocapsid-like particles (NLPs) in vitro. The specificity and propensity of C124 to the assembly and its implications on HCV pathogenesis are not well understood.MethodsSpectroscopic techniques, transmission electron microscopy and calorimetry were used to better understand the propensity of C124 to fold or to multimerize into NLPs when subjected to different conditions or in the presence of unspecific nucleic acids of equivalent size to cellular microRNAs.ResultsThe structural analysis indicated that C124 has low propensity to self-folding. On the other hand, for the first time, we show that C124, in the absence of nucleic acids, multimerizes into empty NLPs when subjected to a pH close to its isoelectric point (pH ≈ 12), indicating that assembly is mainly driven by charge neutralization. Isothermal calorimetry data showed that the assembly of NLPs promoted by nucleic acids is enthalpy driven. Additionally, data obtained from fluorescence correlation spectroscopy show that C124, in nanomolar range, was able to interact and to sequester a large number of short unspecific nucleic acids into NLPs.DiscussionTogether, our data showed that the charge neutralization is the major factor for the nucleocapsid-like particles assembly from C-terminal truncated HCV core protein. This finding suggests that HCV core protein may physically interact with unspecific cellular polyanions, which may correspond to microRNAs and mRNAs in a host cell infected by HCV, triggering their confinement into infectious particles.

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Phytolacca americana lectin (Pa-2; pokeweed mitogen): an intrinsically unordered protein and its conversion into partial order at low pH

Cited by 14 publications

References 39 publications

Monomeric Banana Lectin at Acidic pH Overrules Conformational Stability of Its Native Dimeric Form

Monomeric Banana Lectin at Acidic pH Overrules Conformational Stability of Its Native Dimeric Form

pH-Dependent Conformational Transitions in Conalbumin (Ovotransferrin), a Metalloproteinase from Hen Egg White

Charge neutralization as the major factor for the assembly of nucleocapsid-like particles from C-terminal truncated hepatitis C virus core protein

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