Structural aberrations in T-even bacteriophage: II. Characterization of the proteins contained in aberrant heads

Abstract

The composition of normal heads, short heads, and polyheads obtained from T-even bacteriophages was examined. It was found that normal heads and short heads each contained three classes of structural proteins of 43,000, 18,000, and 11,000 daltons molecular weight. Short heads obtained from a T4D amber mutant in gene 66 and those induced with proflavin, triazolealanine, or putrescine in T4B, contained relatively more of the 18,000 dalton subunit class than did the normal heads. Tubular polyheads obtained using a T4D amber mutant in gene 20 and those obtained by induction with l-canavanine in T4B, were composed of a subunit class with a molecular weight of 54,000–60,000 daltons and very little, if any, of the other two subunit classes. Multilayered polyheads obtained from a T4D amber mutant in gene 22 also contained a subunit class of 54,000 daltons, little of the 11,000 class subunit, and a small amount of the 18,000 class subunit. From information obtained by amino acid analyses and isoelectric points it was concluded that the 54,000 dalton subunit did not yield both the 43,000 and 11,000 dalton structural proteins as degradation products. A model of the structure of normal and aberrant heads was presented which accounted for the varying amounts of the proteins contained in these structures. The reaggregation behavior of the three classes of structural proteins was also studied, and it was found that the 43,000 subunit class readily formed aggregates with the exclusion of both the 18,000 and 11,000 dalton subunits, but these aggregates did not resemble recognizable head structures.