In some of the L3 phages the chaperone protein frameshift is annotated as a +1 frameshift and in others it is annotated as a -2 frameshift. When annotated as a -2 frameshift, the sequence is HFFFGSK. When annotated as a +1 frameshift the sequence is HFFGSK. Both seem equally feasible. Is there any mass spec evidence that one is more likely than the other? The slippery sequence is TTTTTTC…but it involves a shift from the 2nd reading frame to the 1st instead of a shift from the 2nd reading frame to the 3rd.