Robert Bost and Richard Cribbs studied a strain of E. coli (araB14) that possessed a nonsense mutation in the structural gene that encodes Lribulokinase, an enzyme that allows the bacteria to metabolize the sugar arabinose (R. Bost and R. Cribbs. 1969. Genetics 62:1–8). From the araB14 strain, they isolated some bacteria that possessed mutations that caused them to revert back to the wild type. Genetic analysis of these revertants showed that they possessed two different suppressor mutations. One suppressor mutation (R1) was linked to the original mutation in L-ribulokinase and probably occurred at the same locus. By itself, this mutation allowed the production of L-ribulokinase, but the enzyme produced was not as effective in metabolizing arabinose as the enzyme encoded by the wild-type allele. The second suppressor mutation (SuB) was not linked to the original mutation. In conjunction with the R1 mutation, SuB allowed the production of L-ribulokinase, but SuB by itself was not able to suppress the original mutation. Q. Propose an explanation for how R1 and SuB restore the ability of araB14 to metabolize arabinose and why SuB is able to more fully restore this ability.
Robert Bost and Richard Cribbs studied a strain of E. coli (araB14) that possessed a nonsense mutation in the structural gene that encodes Lribulokinase, an enzyme that allows the bacteria to
Q. Propose an explanation for how R1 and SuB restore the ability of araB14 to metabolize arabinose and why SuB is able to more fully restore this ability.
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