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Bacteriophage lambda tail assembly chaperone, TAC, protein G This family consists of Bacteriophage lambda minor tail protein G and related sequences. The construction of phage tails involves a stage of tail-tube formation, and tail-tube polymerization requires two additional proteins, gpG and gpGT. The open reading frames, ORFs, for gpG and gpGT are overlapping and are related by a programmed translational frameshift. During virion morphogenesis, gpG is expressed in large amounts, and about 3.5% of the time, a -1 translational frameshift leads to the production of the larger fusion protein, gpGT. The correct ratio of gpG to gpGT, as determined by the frequency of frameshifting, is crucial for tail assembly. Since gpG accumulates to high levels during a lambda infection and yet is not found in mature phage particles it is believed to act as a chaperone.
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