| Molecular chaperones or heat-shock proteins perform vital cellular functions under normal conditions, as well as protect cells against stress induced damage. The stress-proteins, HSP70 and HSP80, of Neurospora crassa are characterized in this study. The oligomeric state of purified HSP70 and HSP80 was investigated using dynamic light scattering. Both chaperones were shown to form a wide range of high molecular mass, soluble, protein aggregates. A direct interaction between HSP70 and HSP80 was demonstrated by partial tryptic digestion and surface plasmon resonance. Proteolytic digestion experiments revealed that binding of nucleotides induces conformational changes in HSP70, HSP80 and the [HSP70-HSP80] complex. The chaperoning abilities of HSP70, HSP80 and [HSP70-HSP80] were demonstrated in vitro by the protection of both pyruvate kinase from thermal inactivation and citrate synthase from thermal aggregation. The binding of nucleotides was shown to modulate the oligomeric state, chaperoning functions and hetero-oligomeric complex formation abilities of HSP70 and HSP80. |
