Destabilization of Lysozyme and chaperone like action of alpha crystallin isolated from goat’s eye lens was investigated at various temperature ranges in phosphate buffer (pH 7.1) solution and dithiothretol (DTT). This was monitored spectrophotometrically at 260nm. The heat and DTT-induced destabilization of lysozyme was prevented by alpha crystallin in a concentration dependent manner. Alpha crystallin like other chaperones, fulfils its chaperone like action in preventing aggregation of denatured proteins by the formation of complexes.
1.0 INTRODUCTION AND LITERATURE REVIEW
Proteins are the workhorses of the living cell. Although proteins may differ in sequence, shape and function, but have in common, the same stereo configuration (i.e. they all have to fold into specific three-dimensional structures) which are mandatory for proper function (Bruce et al., 2002). Protein structures however are not rigid, but have a dynamic life style, which may involve unfolding and refolding, complex association and dissociation (Anfisen, 1972). Stress and also many physiological events require proteins to surrender their structure or to regain it at a later stage. A very large number of distinct conformations exist for the polypeptide chain of which a protein spends most of its time in the native conformation, which spans only an extremely small fraction of the entire configuration space. Thus, the amino acid sequence of proteins must satisfy two requirements: one, thermodynamics and the other kinetic. The thermodynamics requirement is that the sequence must have a unique folded conformation, which is stable under physiological conditions.
Most proteins can be denatured by heat, which has complex effect on the weak interactions in proteins (Vandenberg et al., 2000). If the existing temperature is increased slowly, a protein conformation generally remains intact until an abrupt loss of structure and function occurs over a narrow temperature range (Nelson and Cox, 2008). The spatial arrangement of atoms in a protein is called its conformation (Deechongkit et al., 2004).