Protein truncation test (PTT)

This is a test for frameshift, splice, or nonsense
mutations that leads to a truncated protein due
to an early stop codon created downstream of
the mutation. The truncated protein is detected
in an assay based on an in-vitro translation system.
The translation will be interrupted at a
premature stop codon resulting from the mutation.
The size of the newly translated protein is
determined by gel electrophoresis. PTT detects
the approximate location of the mutation as reflected
by the size of the mutant protein. PTT is
useful in studying genes with frequent nonsense
mutations, such as the APC, BRCA1, and
BRCA2 genes. However, it cannot be applied for
genes with frequent missense mutations.