Assembly of type I collagen fibrils de novo. Between 37 and 41 degrees C the process is limited by micro-unfolding of monomers.
The effects of temperature on the assembly of collagen fibrils were examined in a system in which collagen monomers are generated de novo and in a physiological buffer by specific enzymic cleavage of type I pC-collagen, an intermediate in the normal processing of type I procollagen to type I collagen. Increasing the temperature of the reaction in the range of 29-35 degrees C decreased the turbidity lag and increased the rate of propagation as assayed by turbidity. The effect of temperature on the turbidity propagation rate gave a linear Arrhenius plot with a negative slope. The predicted value of the activation energy of propagation was 113 kJ/mol. However, the effects of temperature on the rate of assembly above 37 degrees C were opposite to the effects seen at temperatures below 37 degrees C. In the range of 37-41 degrees C, the turbidity propagation rate decreased markedly with temperature. Also, the turbidity lag increased. Therefore, much longer times were required for monomers to reach equilibrium with fibrils. A large fraction of the collagen monomers remaining in solution at temperatures above 37 degrees C was sensitive to rapid digestion by trypsin and alpha-chymotrypsin. Cooling the solutions to 25 degrees C made the monomers resistant to protease digestion. The results are consistent with the conclusion that, although formation of collagen fibrils is a classical example of an entropy-driven process of self-assembly, the rate of assembly between 37 and 41 degrees C is limited by reversible micro-unfolding of the monomer.
Kadler
K E
KE
Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.
Hojima
Y
Y
Prockop
D J
DJ
D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D046911:Macromolecular Substances; D011347:Procollagen / Q000378:metabolism; D011487:Protein Conformation; D011489:Protein Denaturation; D012867:Skin / Q000378:metabolism; D013816:Thermodynamics
D046911:Macromolecular Substances; D011347:Procollagen; D003094:Collagen