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

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Abstract

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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Abbreviations

ANS:

1-anilino-8-napthalene sulfonate

CA:

Conalbumin

DLS:

Dynamic light scattering

GnHCl:

Guanidine hydrochloride

MG:

Molten globule

MRE:

Mean residue ellipticity

P d :

Polydispersity

T m :

Mid-point temperature

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Acknowledgments

This work was supported by the Council of Scientific and Industrial Research (CSIR) funded project New Delhi, India grant No. 37(1456)/10/EMR-II. G. Rabbani acknowledged CSIR, New Delhi, India for financial assistance in the form of Senior Research Fellow (SRF). A. H. Khan, University of Glasgow, Scotland is greatly acknowledged for the editing and valuable suggestions during the preparation of this manuscript.

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  1. Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, 202 002, India

    Gulam Rabbani, Ejaz Ahmad, Nida Zaidi & Rizwan Hasan Khan

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  1. Gulam Rabbani
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  2. Ejaz Ahmad
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Correspondence to Rizwan Hasan Khan.

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Rabbani, G., Ahmad, E., Zaidi, N. et al. pH-Dependent Conformational Transitions in Conalbumin (Ovotransferrin), a Metalloproteinase from Hen Egg White. Cell Biochem Biophys 61, 551–560 (2011). https://doi.org/10.1007/s12013-011-9237-x

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