RESUMO
Conformational changes in bacteriophage tail proteins after heating and ionic strength alteration leading to dissociation of tail sheath have been studied using protein fluorescence, differential scanning microcalorimetry and electron microscopy methods. Autonomous structural changes in tube-baseplate proteins have been revealed. They take place under the same conditions as those which release the bonds holding the sheath protein subunits to those of the tube in isolated sheathed tails. The conformational changes in the tube-baseplates are reversible similarly to the process of assembly and disassembly of the extended sheath. Morphological changes in the tube have been found at the temperature above the transition registered by protein fluorescence but not by calorimetry. This suggests that revealed spectral alterations reflect changes in quaternary structure of tail tube in particular.
