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

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.

Moderate conformational impact of citrate on ovotransferrin considerably increases its capacity to self-assemble at the interface

“…The near UV spectra of ovotransferrin in citrate and in acetate reveal three negative ellipticity peaks at around 277, 285 and 296 nm and single shoulder at 291 nm. These results are in agreement with those obtained in the literature to the native state of ovotransferrin [7,51]. As can be observed, the peaks at 277, 285 and 291 nm tend to diminish.…”

Calorimetric and spectroscopic binding studies of amoxicillin with human serum albumin

“…There are only three aromatic fluorophores amino acids, tryptophan (Trp), tyrosine (Try) and phenylalanine (Phe) in HSA which are used for studying conformational changes in HSA on drug binding. However, among them contribution of tryptophan is maximum [28,29]. The intrinsic fluorescence of HSA excited at 295 nm is mainly contributed by the Trp residue alone, because the Phe residue has a very low quantum yield and the fluorescence of Tyr is almost totally quenched when it is ionized or nearby to an amino group, a carboxyl group or a Trp [30].…”

Neo-epitopes on crotonaldehyde modified DNA preferably recognize circulating autoantibodies in cancer patients

“…The filtered samples were directly transferred into a 12 μl black quartz cell and DNA concentration was 10 μg ml −1 . For further details, refer to Rabbani et al [23].…”