CONGO RED-STABILIZED INTERMEDIATES IN THE LAMBDA-LIGHT CHAIN TRANSITION FROM NATIVE TO MOLTEN STATE

Disruption of tertiary interaction makes a protein accessible to penet ration by different small molecular compounds. Their interaction may s tabilize the altered protein conformation. Congo red is proposed here as a stabilizer of the molten globule state and also of highly reversi ble intermediates in the transition from native to molten state. Human immunoglobulin lambda light chain (dimer) was used. Two protein-Congo red complexes were found after heating lambda chain in the presence o f Congo red. They differed in the amount of attached dye molecules. Th e binding of dye was interpreted as a two-step dye penetration process involving the peripheral parts of the protein in the first step (at l ower temperatures). It was concluded that the liquid crystal propertie s of Congo red enable it to form specific complexes with proteins, whi ch have become accessible to penetration by ligands after global or lo cal disruption of tertiary interaction. This dye may thus be used as a stabilizer of unfolding intermediates in the step preceding the molte n globule state.