Refolding of partially thermo-unfolded cinnamomin A-chain mediated by B-chain.
The pure cinnamomin A-chain is unstable compared to that in the mixture of A- and B-chain or in intact cinnamomin molecule either being stored at 4 degrees C or being heated. When being heated at 45 degrees C for 20min, the A-chain generates partially unfolded intermediate and loses its tertiary structure as monitored by circular dichroism (CD) and tryptophan fluorescence, thus resulting in the inactivity of its RNA N-glycosidase albeit it retains most of its secondary structures. This partially unfolded intermediate is sensitive to protease, exhibiting property of a molten globule. The changes in conformation and activity are irreversible upon cooling. The partially unfolded intermediate can fully restore its RNA N-glycosidase activity in the presence of cinnamomin B-chain. The phenomenon, that the cinnamomin B-chain mediates the refolding of partially unfolded A-chain, probably plays an important role in the intracellular transport of the cytotoxic protein, i.e., keeping the structural stability of A-chain and refolding partially unfolded A-chain that occasionally appeared in the process of intracellular transport, to avoid the destiny of proteolysis that occurs in most denatured proteins in cell.
Wang
Bao-Zhong
BZ
State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue-yang Road, 200031, Shanghai, China.
Liu
Wang-Yi
WY
D020418:Algal Proteins; D027423:Cinnamomum camphora / Q000737:chemistry; D006358:Hot Temperature; D009699:N-Glycosyl Hydrolases / Q000737:chemistry; D010940:Plant Proteins / Q000737:chemistry*; D011489:Protein Denaturation; D017510:Protein Folding; D021122:Protein Subunits; D011506:Proteins / Q000737:chemistry*; D054790:Ribosome Inactivating Proteins, Type 2; D012270:Ribosomes / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D013816:Thermodynamics; D013820:Thermolysin
D020418:Algal Proteins; D010940:Plant Proteins; D021122:Protein Subunits; D011506:Proteins; D054790:Ribosome Inactivating Proteins, Type 2; C061930:cinnamomin, Phytophthora cinnamomi; D009699:N-Glycosyl Hydrolases; D013820:Thermolysin