Structural localization of the proteins of the head to tail connecting region of bacteriophage phi 29.

The head to tail connector of bacteriophage phi 29 has been studied to locate its two structural proteins (p10 and p11). Treatment with trypsin led to proteolysis of p10 while p11 remained intact. Computer filtration of electron micrographs of crystals of trypsinized necks showed a change in the external 12-fold area of the neck when compared with control necks. Proteolized necks completely released p10 after treatment with low concentrations of an ionic detergent. The resulting structures, containing p11, showed similarity with the central area of the neck (seen in front view) and accounted for the lower collar and the axial extension of the neck (seen in side view). These results, together with the differences found in the proteolysis of p10 in necks with and without appendages, lead to a model for the neck region of phi 29 in which p10 makes the upper collar (and the external 12-fold area of the neck seen in front view), while p11 forms the lower collar and the axial extension (the inner region of the neck seen in front view).