Thermal stability of human plasma fibronectin and its constituent domains.

摘要: Human plasma fibronectin undergoes thermal denaturation with a midpoint between 62 and 64 degrees C. The irreversible transition is characterized by an increase in the intensity wavelength of intrinsic tryptophan fluorescence, ability to enhance fluorescence 1,8-anilinonaphthalene sulfonate, polarization covalently attached fluorescein. Addition molecules which bind high affinity, e.g. gelatin or heparin, had no stabilizing effect. This was attributed presence multiple domains, all must be stabilized prevent aggregation. Further support for this interpretation came from studies six different proteolytic fragments collectively span almost entire molecule. Cell-binding derived central regions chain were least stable, exhibiting behavior similar that whole protein. Fragments C-terminal more stable 7-8 C, those N-terminal region showed any parameters up 85 C some experiments. A fluorescein-labeled 60-kilodalton gelatin-binding fragment been heated 70 produced upon addition Kd = 1.3 X 10(-7) M, unheated control. spectra maxima decreased progressively 335 nm at N terminus 313 terminus. These observations further elaborate multidomain structure human reveal significant differences tertiary stabilities various domains.